Luminous intensity distribution control device and display having the same

ABSTRACT

There is eliminated a fringe pattern produced at the time of incidence of polarized light of a light distribution control element, in which stray light derived from outside unnecessary light in a liquid crystal display apparatus or the like can be effectively reduced, and bright, wide viewing angle characteristics are achieved as viewed at any angle by an observer. 
     In the light distribution control element ( 100 ) constituted of a transparent base member ( 104 ), an array of a plurality of micro-lenses (transparent beads  105 ) densely arranged on the transparent base member and a light absorbing layer having very small opening portions substantially at focal positions of the micro-lenses, the transparent base member is constituted of a transparent body which is substantially isotropic optically or a transparent body having uniaxial optical anisotropy.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a §53(b) continuation of U.S. application Ser. No. 09/743,495filed 10 Jan. 2001 and issued as U.S. Pat. No. 6,650,472 B1, which is a§371 national stage of PCT/JP99/03593 filed 2 Jul. 1999, and thiscontinuation is related to U.S. application Ser. No. 10/642,225 filed 18Aug. 2003, pending.

TECHNICAL FIELD

The present invention relates to a light distribution control elementwhich can be used as a transmission type screen member of a rearprojection type display apparatus or a viewing angle expanding member ofa liquid crystal display apparatus or the like, and a display apparatususing the light distribution control element.

BACKGROUND ART

A rear projection type display apparatus can comparatively easilyrealize large screen display in a reduced size and at a low cost incomparison with a direct sight type CRT, and therefore, its demand isincreasing centering on North American markets. Particularly, unlike arear projection type display apparatus using a CRT projection tube,highly fine display without any blur can be carried out to peripheralportions of a screen by dot matrix display, according to a rearprojection type display apparatus having a projecting apparatus using aliquid crystal display element of a TN (Twisted Nematic) liquid crystalor the like as a two-dimensional optical switch element, and therefore,such a rear projection type display apparatus is expected as aprospective product of a high resolution digital television.

FIG. 11 is a schematic sectional view of a rear projection type displayapparatus. A transmission type screen 703 is irradiated with a projectedlight beam 704 emitted from a projecting apparatus 701 via a mirror 702,and an image is displayed on a front face thereof.

As shown in FIG. 38, the transmission type screen 703 is normallyconstituted of a Fresnel lens sheet 1402 and a lenticular lens sheet1401, and the Fresnel lens sheet 1402 is an optical part which operatessimilarly to a convex lens and functions of widening a suitable viewingrange by bending a direction of a main light beam from the projectingapparatus 701 toward an observer.

The lenticular lens 1401 effectively distributes a limited projectedlight flux from the projecting apparatus 701 to an observing range ofthe observer to thereby provide a bright image as its object.

FIG. 36 is a schematic sectional view showing an example of a lenticularlens, and FIG. 37 is a schematic perspective view of the lenticularlens.

In the lenticular lens 1401, a plurality of cylindrical lenses 1501 arearrayed in one direction and black stripes 1502 are provided at portionsother than portions for condensing a light beam, thereby restraining acontrast ratio with regard to an ambient light beam from loweringwithout any loss of the projected light beam ideally by disposing focalpositions of the lenses 1501 on an observing face of a screen.

Generally, by arraying the lenticular lenses such that generatorsthereof are directed orthogonally to a display face, a wide viewingangle is provided in the horizontal direction. Therefore, a light beamis distributed in the vertical direction only by diffusion by adiffusing member blended in a base material of the lenticular lenses orsurface portions thereof, and accordingly, a viewing angle in thevertical direction is considerably narrower than that in the horizontaldirection. Further, according to the lenticular lens, lenses having alinear shape are regularly arranged, and therefore, moire interferencefringe is liable to occur on the image.

In contrast thereto, Japanese Unexamined Patent Publication No. 2-77736discloses a transmission type screen having a constitution in which atransparent base member 1601 is covered with spherical lenses 1602 whichare fixed by a transparent resin, as shown in FIG. 39. According to theconstitution, no die is used, and therefore, there is no restriction insize in view of fabrication and a seamless transmission type screenhaving a large screen can be realized. Further, a light beam incidentfrom a side of the spherical lenses is converged by the lens effect ofthe spherical lenses and is diverged isotropically, and therefore, wideviewing angles are provided both in the horizontal and verticaldirections.

Further, there is published a screen having a structure in which opticalbeads are fixedly attached on a transparent base member via alight-absorbing adhering agent layer and surfaces of the optical beadson the opposite side of the transparent base member are back-coatedtransparently in SID94 DIGEST pp. 741-744 (A Novel High-ResolutionAmbient-Light-Rejecting Rear-Projection Screen).

Further, Japanese Unexamined Patent Publication No. 9-318801 discloses aplane type lens having a structure in which very small sphericaltransparent beads are fixed on a transparent base member by a coloredhot melt adhering agent layer and a transparent hot melt adhering agentlayer. According to the structure, like Japanese Unexamined PatentPublication No. 2-77736, by the lens effect of the beads, there isprovided isotropic viewing angles which are wide both in the horizontaland vertical directions. Further, an unnecessary light beam incidentfrom outside is absorbed by a light-absorbing adhering agent layer (orcolored hot melt adhering agent layer), and therefore, a high contrastratio is provided even in a bright environment. Further, high resolutioncan be realized comparatively easily by reducing the diameter of thebead.

The above-described conventional plane type lens (hereinafter, referredto as a light distribution control element) is fabricated as follows: aflat polyethylene terephthalate (PET) resin film having a thickness of120 μm is used as the transparent base member; a transparent adheringagent layer comprising a polyester-based hot melt adhering agent isformed in a thickness of 5 μm on a surface of the resin film; a coloredadhering agent layer, in which the same polyester-based hot meltadhering agent is blended with 10 parts by weight of carbon black, isformed on the transparent adhering agent layer; and the entirety issolidified once.

Spherical transparent beads made of glass having a refractive index of1.935 (wavelength: 589.3 nm) and a diameter of 50 μm are denselyarranged to be dispersed on the entirety. While heating to soften thetransparent adhering agent layer and the colored adhering agent layer ina thermostatic chamber, the transparent beads are pressed toward thetransparent base member by a pressing plate, to thereby make thetransparent beads embed in and fixedly adhere to the colored adheringagent layer and the transparent adhering agent layer. The thickness ofthe adhering layer after fixation is about 21 μm by adding those of thetransparent adhering agent layer and the colored adhering agent layer,and the transparent beads are exposed from the adhering agent layer byabout 58% of a diameter thereof.

When the fabricated light distribution control element is evaluated as atransmission type screen of a rear projection type display apparatushaving a projecting apparatus using a TN type liquid crystal displayelement as a two-dimensional optical switch element (light bulb), thereare provided wide viewing angles equal to or larger than 50 degree (inthis case, an angle giving a brightness half of a front brightness) bothin the horizontal direction and the vertical direction, and anunnecessary light beam incident from outside (an observer side) on thelight distribution control element is absorbed by the colored adheringagent layer and black display at low brightness can be realized evenunder bright environment.

However, when an image projected on the light distribution controlelement is observed in an oblique direction, it is found that a fringepattern substantially in shapes of concentric circles emerges and theimage quality is significantly deteriorated. Further, it is also foundthat when observed in an oblique direction, a change in chromaticityunfavorable to the image is caused.

It is an object of the present invention to provide a light distributioncontrol element without inducing any deterioration in image qualitycaused by occurrence of the above-described fringe pattern and a displayapparatus having the high brightness, high contrast ratio and highviewing angle using the light distribution control element. Objectsother than the above-described object will become apparentself-evidently from the following description.

DISCLOSURE OF INVENTION

The inventors have investigated in further details on theabove-described conventional light distribution control element in orderto find the cause of the occurrence of fringe patterns and the change inchromaticity. As a result, it has been found that the fringe pattern isproduced when polarized light is incident on the light distributioncontrol element, various phase differences are produced in lightprogressing at different angles in a transparent base member owing tooptical anisotropy of the base member and the fringe pattern is producedby a difference between energy transmittances of a p polarized lightcomponent and an s polarized light component of light emitted from thetransparent base member in combination with the phase difference.Further, it has been found that the change in chromaticity is causedsince the light distribution characteristic of the light distributioncontrol element is changed depending on the polarized state of incidentlight. The following is the gist of the present invention reached basedupon the above-described findings.

[1] There is provided a light distribution control element including atransparent base member, a number of micro-lenses densely arranged onone face of the transparent base member and a light absorbing layerhaving very small opening portions substantially at focal positions ofthe micro-lenses, wherein the light distribution control element ischaracterized in that the transparent base member is constituted of atransparent body which is substantially isotropic optically or atransparent body having uniaxial optical anisotropy.

By using the light distribution control element, occurrence of a fringepattern at the time of the incidence of polarized light is eliminated byrestraining a phase difference influenced on an image quality from beingcaused.

[2] There is provided a rear projection type display apparatus includinga projecting apparatus for projecting an optical image and atransmission type screen, on a rear face of which projected light fromthe projecting apparatus is incident, for displaying the projected lightat a front face thereof, a rear projection type display apparatuscharacterized in that the projecting apparatus comprises a single tubetype projecting apparatus having a light source, two-dimensional opticalswitch elements for modulating light from the light source into anoptical image in accordance with image information and a projecting lensfor enlarging and projecting the optical image after the modulation, andfurther comprises polarized light state aligning means for makingpolarized states of optical image lights formed by the two-dimensionaloptical switch elements substantially coincide with each other over theentire region of visible wavelengths when the optical image after themodulation emitted from the projecting apparatus is incident on thetransmission type screen; and the transmission type screen isconstituted of a light distribution control element including atransparent base member, a number of micro-lenses densely arranged onone face of the transparent base member and a light absorbing layerhaving very small opening portions substantially at focal positions ofthe micro-lenses, the transparent base member being constituted of atransparent body which is substantially isotropic optically or atransparent body having uniaxial optical anisotropy, and light fluxcollimating means provided on a projected light incident side of thelight distribution control element.

As described above, the polarized states of the projected lightsincident on the light distribution control elements (optical imagelights) coincide with each other in the entire region of visiblewavelengths. Accordingly, there is caused no staining derived frompolarized light dependency of light distribution characteristics of thelight distribution control element, and there can be realized displayhaving a high image quality without any change in chromaticity evenobserved in an oblique direction.

Further, image light incident on the light distribution control elementis brought into a substantially parallel state and is incident thereonsubstantially at an angle of incidence of 0 degree, and accordingly,there is provided a bright display image by restraining transmittance ofthe light distribution control element from lowering.

[3] There is provided the rear projection type display apparatus,wherein the two-dimensional optical switch element is a two-dimensionaloptical switch element for executing display by utilizing polarizedlight, the two-dimensional optical switch element comprising polarizedlight state converting means for converting a polarized light state ofoptical image light formed by the two-dimensional optical switch elementinto any of a polarized light state of linearly polarized light havingan oscillation direction of an electric vector directed in a horizontaldirection relative to a display face of the transmission type screen,linearly polarized light directed in a vertical direction, circularlypolarized light and elliptically polarized light.

As described above, the polarized light state of the optical image lightincident on the light distribution control element can be controlled,and accordingly, there can be realized the rear projection type displayapparatus in which the viewing angle characteristic can easily bechanged by the polarized light dependency of the light distributioncharacteristic of the light distribution control element even when theconstitution of the transmission type screen is not changed.

[4] There is provided the rear projection type display apparatus furthercomprising an observer sensing unit for sensing the presence or absenceof an observer, observer position determining means for determiningpositions of the observer in the horizontal and vertical directions by asensed signal of the observer sensing unit, and control signaloutputting means for outputting a control signal to a polarized lightstate converting element based on information of the observer positiondetermining means.

As described above, there can be provided the viewing anglecharacteristic in accordance with the positions of the observer byautomatically determining the positions of the observer and changing thepolarized light state of projected light based on the positioninformation. That is, the viewing angle characteristic is automaticallychanged in accordance with the positions of the observer, limited imagelight is effectively distributed in a direction of the observer andexcellent image is provided to the observer.

[5] There is provided the rear projection type display apparatusfeatured in that the projecting apparatus comprises a single tube typeprojecting apparatus having a light source, two-dimensional opticalswitch elements for modulating light from the light source into anoptical image in accordance with image information and a projecting lensfor enlarging and projecting the optical image after the modulation, thetransmission type screen comprises a light distribution control elementhaving a transparent base member, a number of micro-lenses denselyarranged on one face of the transparent base member and a lightabsorbing layer having very small opening portions substantially atfocal positions of the micro-lenses and light flux collimating meansarranged on a projected light incident side of the light distributioncontrol element, and further comprises unpolarized light forming meansfor converting projected light emitted from the projecting apparatus andincident on the transmission type screen into substantially unpolarizedlight.

As described above, the optical image light incident on the lightdistribution control element constituting the transmission type screenis converted into the unpolarized light, and accordingly, there iscaused no change in chromaticity derived from the polarized lightdependency of the light distribution characteristic of the lightdistribution control element. Further, there is caused no fringe patternproduced at the time of incidence of polarized light by the opticalanisotropy of the transparent base member of the light distributioncontrol element, and accordingly, there can be provided a beautifulimage without any deterioration in image quality. Further, even when atransparent body having optical anisotropy is used as the transparentbase member, there is no deterioration in image quality, andaccordingly, a range of selecting the material is widened, and there canbe realized the transmission type screen comprising the lightdistribution control element which is further inexpensive and isprovided with high strength.

[6] There is provided a liquid crystal display apparatus including apair of transparent substrates formed of a lamination of transparentelectrodes and orientation films and bonded to each other with aconstant clearance therebetween while orientation films formed facesopposed to each other, a liquid crystal layer enclosed in the clearance,voltage applying means for applying a voltage corresponding to an imagesignal across the transparent electrodes and a polarizer and an analyzerdisposed on a light incident face side and a light emitting face side ofthe pair of transparent substrates,

the liquid crystal display characterized in that a rear face of each ofthe pair of transparent substrates is provided with a backlightapparatus for emitting substantially parallel light and the lightemitting face side of the pair of transparent substrates is providedwith a light distribution control element comprising a transparent basemember, a number of micro-lenses densely arranged on one face of thetransparent base member and a light absorbing layer having very smallopening portions substantially at focal positions of the micro-lenses,the light distribution control element being a light distributioncontrol element in which the transparent base member is constituted of atransparent body which is substantially isotropic optically or atransparent body having uniaxial optical anisotropy.

Thereby, only light within a limited range in the vicinity of the frontface capable of achieving an excellent image quality can beisotropically diverged by the light distribution control element, andaccordingly, there can be realized the liquid crystal display apparatuscapable of providing an image having a high contrast ratio without anychange in chromaticity and no inversion of a gray scale within a wideviewing angle range.

[7] There is provided the liquid crystal display apparatus, wherein thelight incident face side of each of the pair of transparent substratesis provided with a polarizer and the light emitting face side isprovided with an analyzer and the light distribution control element inthis order from a side of the transparent base member, and atransmission axis of linearly polarized light of the analyzer isarranged in a horizontal direction relative to a display face.

In this way, by the polarized light dependency of the light distributioncharacteristic of the light distribution control element, a viewingangle in the horizontal direction becomes wider than that in thevertical direction relative to the display face and limited light can beeffectively distributed to an observer.

[8] There is provided the liquid crystal display apparatus, wherein thelight incident face side of the pair of transparent substrates isprovided with a polarizer, the light emitting face side is provided withan analyzer and the light distribution control element in this orderfrom a side of the transparent substrate, and a phase contrast plate isinterposed between the analyzer and the light distribution controlelement.

Thereby, the polarized state of light incident on the light distributioncontrol element can be arbitrarily changed by the phase contrast platearranged between the analyzer and the light distribution controlelement, and accordingly, only by changing the phase contrast plate, adesired viewing angle can be provided by utilizing the polarized lightdependency of the light distribution characteristic of the lightdistribution control element.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view of a light distribution controlelement according to the present invention.

FIG. 2 is a schematic perspective view of the light distribution controlelement according to the present invention.

FIG. 3 is a schematic sectional view for explaining an example of amethod of fabricating the light distribution control element accordingto the present invention.

FIG. 4 is an equi-brightness diagram showing light emitting(distributing) characteristics of a conventional light distributioncontrol element when polarized light is incident thereon.

FIG. 5 is an explanatory view of a coordinate system of theequi-brightness diagram.

FIG. 6 is an explanatory view of a circular cut surface of an indexellipsoid.

FIG. 7 is an explanatory view of an optical axis of a polyethyleneterephthalate film.

FIG. 8 is a graph showing a relationship between an optical incidentangle and an energy transmission rate of the polyethylene terephthalatefilm.

FIG. 9 is an equi-brightness diagram showing light emittingcharacteristics of a light distribution control element according to thepresent invention when linearly polarized light is incident thereon.

FIG. 10 is a graph showing light emitting (distributing) characteristicsof the light distribution control element according to the presentinvention when linearly polarized light is incident thereon.

FIG. 11 is a schematic sectional view of a rear projection type displayapparatus according to the present invention.

FIG. 12 is a schematic sectional view of a projecting apparatusaccording to a rear projection type display apparatus of the presentinvention.

FIG. 13 is a schematic sectional view of a two-dimensional opticalswitch of the projecting apparatus according to the rear projection typedisplay apparatus of the present invention.

FIG. 14 is a schematic sectional view of a transmission type screenaccording to the rear projection type display apparatus of the presentinvention.

FIG. 15 is a schematic diagram for explaining a dependency of atransmission rate on an optical incident angle according to the lightdistribution control element of the present invention.

FIG. 16 is a graph showing one example of a relationship between atransmission rate and the optical incident angle according to the lightdistribution control element of the present invention.

FIG. 17 is a schematic sectional view of polarized state aligning meansused in a projecting apparatus according to the rear projection typedisplay apparatus of the present invention.

FIG. 18 is a schematic view for explaining operation of the polarizedstate aligning means used in the projecting apparatus according to therear projection type display apparatus of the present invention.

FIG. 19 is a schematic sectional view of a projecting apparatusaccording to a rear projection type display apparatus of the presentinvention.

FIG. 20 is a schematic sectional view of a polarized state convertingelement used in the projecting apparatus according to the rearprojection type display apparatus of the present invention.

FIG. 21 is a schematic view for explaining operation of the polarizedstate converting element used in the projecting apparatus according tothe rear projection type display apparatus of the present invention.

FIG. 22 is a schematic view for explaining operation of a polarizedstate converting element used in a projecting apparatus according to arear projection type display apparatus of the present invention.

FIG. 23 is a schematic view for explaining operation of a polarizedstate converting element used in a projecting apparatus according to arear projection type display apparatus of the present invention.

FIG. 24 is a schematic view for explaining operation of a polarizedstate converting element used in a projecting apparatus according to arear projection type display apparatus of the present invention.

FIG. 25 is a schematic sectional view of a polymer dispersion typeliquid crystal display element of a projecting apparatus according to arear projection type display apparatus of the present invention.

FIG. 26 is a schematic view for explaining operation of the polymerdispersion type liquid crystal display element.

FIG. 27 is a schematic view for explaining an optical system forcarrying out display by the polymer dispersion type liquid crystaldisplay element.

FIG. 28 is a schematic view for explaining the optical system forcarrying out display by the polymer dispersion type liquid crystaldisplay element.

FIG. 29 is a schematic sectional view of a projecting apparatusaccording to a rear projection type display apparatus of the presentinvention.

FIG. 30 is a schematic sectional view of a projecting apparatusaccording to a rear projection type display apparatus of the presentinvention.

FIG. 31 is a schematic sectional view of a liquid crystal displayapparatus according to the present invention.

FIG. 32 is a schematic view for explaining linearly polarized lighttransmitting axes of a polarizer and an analyzer of the liquid crystaldisplay apparatus according to the present invention.

FIG. 33 is a schematic sectional view of a liquid crystal displayapparatus according to the present invention.

FIG. 34 is a schematic sectional view of a light distribution controlelement according to the present invention.

FIG. 35 is a schematic perspective view of a light distribution controlelement according to the present invention.

FIG. 36 is a schematic sectional view showing an example of a lenticularlens sheet.

FIG. 37 is a schematic perspective view showing the example of thelenticular lens sheet.

FIG. 38 is a schematic sectional view showing an example of aconventional transmission type screen.

FIG. 39 is a perspective view of a conventional transmission typescreen.

FIG. 40 is a schematic perspective view of a rear projection typedisplay apparatus according to the present invention.

FIG. 41 is an explanatory view exemplifying a partitioned region sensedby an observer sensing unit of the rear projection type displayapparatus according to the present invention.

FIG. 42 is an explanatory view exemplifying the partitioned regionsensed by the observer sensing unit of the rear projection type displayapparatus according to the present invention.

FIG. 43 is a view for explaining an effect of the rear projection typedisplay apparatus according to the present invention.

FIG. 44 is a view for explaining the effect of the rear projection typedisplay apparatus according to the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

An explanation will be given of embodiments according to the presentinvention in reference to the drawings.

FIG. 1 is a schematic sectional view showing an example of a lightdistribution control element according to the present invention, andFIG. 2 is a schematic perspective view thereof.

The light distribution control element is constituted of a transparentbase member 101, a hot melt adhering agent layer 104 formed on a surfacethereof and a plurality of transparent beads 105 each formed into a verysmall sphere fixed to the adhering agent layer 104.

Although the transparent base member 101 may be a base member in aplate-like shape having a rigidity by itself or a base member in afilm-like shape, it is important to use a transparent body which issubstantially isotropic optically or which is provided with an uniaxialanisotropy having an optical axis in a direction in parallel with theplate face or the film face.

Specifically, there is used a glass plate, a transparent plate which issubstantially isotropic optically such as an acrylic resin plate andwhich is produced by injection molding, or a transparent film which isfabricated by a casting process or an extrusion process or the like anduniaxially elongated as necessary and which is substantially isotropicoptically or which is provided with an optical axis in parallel with thefilm face and composed of a polycarbonate resin, a vinyl chloride resin,a polyester-based resin, a cellulose-based resin, a polyvinyl alcoholresin, a polyolefin resin or the like.

The hot melt adhering agent layer 104 is constituted such that atransparent layer 102 and a colored layer 103 are laminated in thisorder. There is used the adhering agent layer having an adhering forcesufficient for the transparent base member 101 and the transparent beads105. There can be used a hot melt adhering agent composed of anacrylic-based resin, a polyester-based resin, a polyamide-based resin, apolyurethane-based resin or the like. There is used the colored layer103 colored by dispersing a pigment of carbon black or the like on thebasis of these adhering agents or colored by dyeing the layer by adyestuff.

As the transparent bead 105, there is used a spherical bead made ofglass or a transparent resin which is optically isotropic. The higherthe refractive index, the larger the angle of refraction of lightincident on the transparent bead, and accordingly, the wider the lightemitting angle (viewing angle) of the light distribution controlelement. However, a brightness in a front direction is lowered by thatamount, reflection on the surface or the interface between thetransparent base member 101 and air is increased, and a total light raytransmittance is lowered.

Further, in order to efficiently transmit light through an openingportion of the transparent bead 105 on a side of a light emitting face,that is, a portion thereof where the transparent bead 105 is broughtinto contact with the transparent adhering agent layer 102, it isadvantageous to reduce an area of condensing light incident on thetransparent bead on the light emitting face side. In this case, when amedium on a light incident side of the transparent bead is air, bysetting the refractive index to about 1.6 through 2.1, the condensingarea at the light emitting face can be sufficiently reduced. Further, bysetting the above-described refractive index to 1.9 through 2.1, lightcan be condensed with smaller aberration.

The refractive index of the transparent bead 105 is selected to becompatible with characteristics requested to the light distributioncontrol element, that is, specifications of viewing angle and brightness(gain) in view of these conditions. Further, there can also be used amixture of transparent beads having different refractive indices asnecessary.

When the light distribution control element 100 is used as a screen orviewing angle expanding means of a display apparatus, the diameter ofthe transparent bead 105 directly influences on the resolution of adisplayed image. That is, an image displayed by the light distributioncontrol element cannot be resolved to the diameter of the transparentbead 105 or smaller. Therefore, it is necessary to reduce the diameterof the transparent bead to be smaller than a pixel of an image to bedisplayed on the light distribution control element.

Although the smaller diameter of the transparent bead 105 easilyachieves high resolution when the diameter of the transparent bead 105is proximate to a wavelength region of light, a factor of scatteringtransmitted light becomes considerable, brightness or transmittance in afront direction is lowered, and accordingly, the lower limit isprescribed self-evidently.

It is preferable that the diameter of the transparent bead 105 is equalto or smaller than a half of a pixel pitch of a displayed image, andpractically, about 20 through 100 μm. Further, the transparent beads 105are arranged on a surface of the transparent base member 101 uniformlyand at a maximum density, and accordingly, it is preferable that adispersion in the particle size is as small as possible. Actually, whenthe dispersion in the particle size is converged within 10%, thefunction as the light distribution control element is satisfied.

Further, the transparent bead 105 having no air bubbles is preferablesince bubbles staying inside becomes a factor of lowering thetransmittance.

Next, an explanation will be given of a method of fabricating the lightdistribution control element 100 according to the present invention inreference to FIG. 3.

Step (a): A hot melt transparent adhering agent in a heated and moltenstate or dissolved by a solvent or dispersed in a solution in acolloidal form is applied to the transparent base member 101 by, forexample, spin coating, knife coating, roll coating, spray coating orblade coating to thereby form the transparent adhering agent layer 102.

Step (b): The colored adhering agent layer 103 is laminated thereon by amethod similar to that of the transparent adhering agent layer 102 tothereby form the hot melt adhering agent layer 104. At this occasion, inorder to prevent the colored adhering agent layer 103 and thetransparent adhering agent layer 102 from mixing together, in formingthe colored adhering agent layer. 103, when the transparent adheringagent layer 102 is brought into a molten state at high temperatures, thetemperature is lowered by forced cooling or natural cooling. Further,when the transparent adhering agent layer 102 is brought into a moltenstate in a solvent or a state of being dispersed in a colloidal form ina solution, the solvent may be evaporated in desiccator to therebysolidify or partially solidify the transparent adhering agent layer.

Step (c): At least one layer of a plurality of the transparent beads 105is arranged to disperse on the colored adhering agent layer 103 suchthat a maximum packing density is achieved. At this occasion, thecolored adhering agent layer 103 is not provided with an adheringproperty in the solidified or partially solidified state, andaccordingly, the transparent beads 105 can be comparatively easilyarranged to disperse at the maximum packing density.

Step (d): Subsequently, the above-described layer is heated by heatingmeans such as a thermostatic chamber or an infrared ray heater tothereby soften and melt the hot melt adhering agent layer 104 and thetransparent beads 105 are embedded into the hot melt adhering agentlayer 104, toward the transparent base member 101 by their own weightsor pressing means.

Step (e): In a state where the transparent beads 105 are embedded, thetemperature of the hot melt adhering agent layer 104 is lowered tonormal temperature to thereby solidify the hot melt adhering agent layerand fixedly adhere the transparent beads thereto.

Further, it is preferable to set the depth of embedding the transparentbeads 105 into the hot melt adhering agent layer 104 such that 50through 80% of the diameter of the bead is exposed. When the amount ofexposure is smaller than that, an amount of light incident on thetransparent bead is lowered owing to absorption by the colored adheringagent layer, and the transmittance is lowered. When the amount ofexposure is larger than that, the function of fixedly adhering the beadsbecomes insufficient.

As described above, steps, there can be provided the light distributioncontrol element according to the present invention, in which one layerof the transparent beads 105 is arranged to disperse substantially atthe maximum packing density and a half or more of the diameter isfixedly exposed from the hot melt adhering agent layer 104 to the lightincident side.

Next, an explanation will be given of optical operation of the lightdistribution control element according to the present invention inreference to FIG. 1. According to the light distribution control element100, as described above, one layer of the transparent beads 105 isarranged to disperse on the light incident face side substantially atthe maximum packing density, and a half or more of the diameter of thebead is fixedly exposed from the hot melt adhering agent layer 104 tothe light incident side.

Therefore, although a portion of parallel incident light 106 verticallyincident on the light distribution control element 100 is absorbed bythe colored adhering agent layer 103 at gaps among the transparent beads105, most of the incident light is incident on the transparent beads105. The incident light transmits through an opening portion formed at aportion where the transparent bead 105 is brought into contact with thetransparent adhering agent layer 102 while being converged by refractingaction of the transparent bead 105 and is emitted while transmitting anddiverging through the transparent base member 101. That is, lightincident on the transparent bead is converged by the lens effect of thetransparent bead and is isotropically diverged, and accordingly, thereis provided the light distribution control element having an isotropicand wide viewing angle.

Further, unnecessary light 107 incident from outside is absorbed by thecolored adhering agent layer 102 and the unnecessary light becomes straylight and is not observed. Therefore, there can be provided the lightdistribution control element having an excellent effect of reducingstray light derived from outside unnecessary light even under a brightenvironment and an isotropic viewing angle characteristic in which theelement is bright when viewed from any angle by an observer.

[Elimination of Fringe Pattern at the Time of Incidence of PolarizedLight]

Next, in order to clarify an effect particular to the light distributioncontrol element according to the present invention, an explanation willbe given of occurrence of a fringe pattern which emerges when observedin an oblique direction at the time of incidence of polarized light,which has been the conventional problem.

FIG. 4 is an equi-brightness diagram representing light emittingcharacteristics at the time of incidence of polarized light in aconventional light distribution control element (in which noconsideration is given to the problem related to the present invention).

The equi-brightness diagram is displayed by connecting points havingequal brightness at intervals of 10% with maximum brightness as 100% ina coordinate system constituted of an emitting angle and an azimuthangle shown in FIG. 5.

In FIG. 4, the central portion designates an emitting angle of 0 degree(front face) and concentric circles of dotted lines show emitting angles(at intervals of 10 degree). Further, the azimuth angle is designated toincrease in the counterclockwise direction with a downward direction ofthe drawing sheet as 0 degree.

As shown in FIG. 4, when polarized light is incident on the conventionallight distribution control element, there emerges a variation in thebrightness substantially in the concentric shape centering on two pointsin the vicinity of an emitting angle of 40 degree. This can be visuallyrecognized actually as a fringe pattern when observed in an obliquedirection.

According to the conventional light distribution control element used inthe measurement, there is used a flat polyethylene terephthalate (PET)film having a thickness of 120 μm as the transparent base member 101.There are formed 5 μm of a transparent adhering agent layer comprising apolyester-based hot melt adhering agent and 4.5 μm of a colored adheringagent layer in which 10 parts by weight of carbon black is blended to apolyester-based hot melt adhering agent on the transparent adheringagent layer and transparent spherical glass beads each having arefractive index of 1.935 (wavelength: 589.3 nm) and a diameter of 50 μmare densely arranged to disperse on the colored adhering agent layer andembedded in and fixedly attached to the adhering agent layers.

A thickness of the adhering layer after fixedly attached with thetransparent beads is about 21 μm including those of the transparentlayer and the colored layer and about 58% of the diameter of thetransparent beads is exposed from the adhering agent layer.

In this case, there is used a PET film which is biaxially elongated asthe transparent base member 101 in the above-described lightdistribution control element. This is because according to the biaxiallyelongated film, in comparison with a non-elongated film, physicalproperties are significantly promoted such that tensile strength andimpact strength are increased and transparency and a range oftemperature of use are also improved. Further, the PET film is providedwith excellent adherence with a polyester-based hot melt adhering agenthaving excellent adhering performance with transparent glass beads andis provided with excellent solvent resistance against theabove-described hot melt adhering agent (solvent: toluene).

Although the biaxially-elongated PET film is used for the transparentbase member from the above-described reason, generally, abiaxially-elongated film comprises a substance having biaxial anisotropyin which three main refractive indices (direction orthogonal to filmface: Z-axial direction, directions in parallel with film face andorthogonal with each other: X-axis and Y-axial directions) differ fromeach other.

The bilateral anisotropy is a property of a substance in whichconsidering an index ellipsoid as shown in FIG. 6, a shape of a cut facethereof is circular, and there are determined two directions ofdirections producing no refractive index anisotropy.

The direction of light is referred to as an optical axis. Since there isno anisotropy of refractive index at the optical axis, there is causedno phase difference in polarized light progressing in paralleltherewith. For example, in the case of the PET film used in theabove-described conventional example, three main refractive indices arenx=1.678, ny=1.645, nz=1.497. As shown in FIG. 7, there are two ofoptical axes in ZX plane forming an angle of 23.3 degree with respect toZ-axis.

Light progressing along the optical axes in the PET film is refracted atan interface with air and is emitted at an emitting angle of 41.6degree, and therefore, substantially the central positions of thevariation of the brightness in the vicinity of the emitting angle 40degree shown in FIG. 4 correspond to the optical axes.

Now, consider the case where light in a particular polarized state(linearly polarized light or elliptically polarized light) is incidenton the light distribution control element. In this case, most of lightincident on the light distribution control element is converged by thetransparent beads, thereafter, is diverged and progresses in the PETfilm at various angles. At this occasion, light progressing along theoptical axes in the PET film does not cause phase differences and thepolarized state remains unchanged.

However, light progressing at an angle deviated from the optical axescauses phase differences in correspondence with the deviation of theangle, and accordingly, a polarized state, that is, a rate of a ppolarized light component in parallel with the light incident face and spolarized light component orthogonal thereto, is changed at theinterface on the light emitting side of the PET film. That is, accordingto the light progressing in a direction different from directions of theoptical axes, in correspondence with the magnitude of the deviation fromthe optical axes, light having much of the p polarized light componentand light having much of the s polarized light component emergealternately.

In this case, generally, in refraction at a surface of a dielectricbody, there is produced a difference in energy transmittance between ppolarized light and s polarized light. FIG. 8 exemplifies the differencein the energy transmittance between p polarized light and s polarizedlight and is a graph showing a relationship between the light incidentangle and the energy transmittance when light progresses from the PETfilm into air.

As shown in FIG. 8, a maximum of 30% or higher of the difference in thetransmittance is produced between p polarized light and s polarizedlight.

Accordingly, there is produced a difference in a transmitted lightamount between lights having much of the p polarized light component andthe s polarized light component and bright and dark in the brightness isprovided, which is visually recognized as the fringe pattern.

Particularly, in a light distribution control element using micro-lensesrepresented by transparent beads, light incident on the micro-lens isconverged and progresses in a transparent base member at various angleswhile being diverged, and accordingly, non-uniformity (variation) in thebrightness of the emitting light is produced very easily by a differencein the phase difference based on a difference in progressing angle oflight in the transparent base member.

The light distribution control element according to the presentinvention is featured in using the transparent base member 101 which issubstantially isotropic optically or which is provided with a substancewith uniaxial anisotropy having an optical axis in parallel with thefilm face. Accordingly, although polarized light incident on the lightdistribution control element is converged by the transparent bead andprogresses at various angles in the transparent base member while beingdiverged, since the transparent base member is optically isotropic,there produces no variation in phase difference owing to the progressingangle, that is, the rate between the p polarized light component and thes polarized light component hardly changes also by the emitting angle,and accordingly, the fringe pattern is not produced.

Further, when polarized light incident on the light distribution controlelement is linearly polarized light, when the transparent base member isof a substance with uniaxial anisotropy having the optical axis in theface, by making a direction of oscillation of an electric vector of theincident linearly polarized light direct in parallel with or orthogonalto a retarded phase axis of the transparent base member, a variation inphase difference produced by the progressing angle of the polarizedlight transmitting through the transparent base member can be reducedand occurrence of the fringe pattern can be restrained.

Further, even when the transparent base member is provided with opticalanisotropy, in the case where the variation in phase difference producedby the progressing angle of light progressing in the transparent basemember is small and a variation in polarized state is small, thevariation in brightness is not visually recognized and is permitted.

For example, when a maximum value of the variation in phase differenceproduced by the difference in progressing angle of light progressing inthe transparent base member is equal to or smaller than a halfwavelength, according to the variation in polarized state produced bythe angle of light transmitting through the transparent base member,even at its maximum, only light having 100% of p polarized statecomponent is converted into light having 100% of s polarized lightcomponent, and accordingly, the change in the brightness is difficult torecognize visually.

More ideally, it is preferable to restrain the maximum value of thevariation in phase difference produced by the angle of lighttransmitting through the transmitting base member is restrained to beequal to or smaller than a quarter wavelength. In this case, even atmaximum, for example, light having 100% of the p polarized lightcomponent is only converted into light having 50% of the p polarizedlight component and 50% of the s polarized light component, andaccordingly, the change in brightness is further difficult to berecognized.

Therefore, the transparent member which is substantially isotropicoptically shows here a member exhibiting isotropy to a degree in whichthe variation in phase difference produced by the difference inprogressing angle of light progressing in the transparent base member issmall, and accordingly, the change in polarized state is also small andthe change in the brightness cannot be recognized.

As described above, according to the light distribution control elementof the present invention, there is used a transparent body which issubstantially isotropic optically or which is provided with the uniaxialanisotropy having the optical axis in the face as the transparent basemember, and accordingly, even when polarized light is incident thereon,no deterioration in the image quality is caused by occurrence of thefringe pattern and a wide viewing angle is provided.

Further, the unnecessary light 107 incident from outside on the lightdistribution control element 100 is absorbed by the colored adheringagent layer 102, and accordingly, the unnecessary light becomes straylight and is not observed. Therefore, stray light derived from outsideunnecessary light is reduced even under a bright environment.

Further, as described above, the energy transmittance of the surface ofthe dielectric body differs between p polarized light and s polarizedlight, and therefore, the transmittance of the p polarized lightcomponent is high and the transmittance of light of the s polarizedlight component is low at the surface of the transparent base member101. As a result, there is produced anisotropy in the light distributioncharacteristics of the emitting light in accordance with the polarizedstate of the incident light.

For example, when linearly polarized light is incident on the lightdistribution control element, a viewing angle in a direction in parallelwith the oscillation direction of the electric vector of the linearlypolarized light is wider than that in a direction orthogonal thereto. Byutilizing the characteristics, a viewing angle in the horizontaldirection can be made larger than a viewing angle in the verticaldirection by making linearly polarized light having the oscillationdirection of the electric vector in the horizontal direction incident onthe light distribution control element.

To the contrary, by making the oscillation direction of the electricvector of incident linearly polarized light vertical, the viewing anglein the vertical direction can be made larger than the viewing angle inthe horizontal direction. Further, by constituting light incident on thepolarized light control element of circularly polarized light, anisotropic viewing angle can also be provided.

That is, according to the light distribution control element of thepresent invention, by controlling the polarized state of light to beincident thereon, the viewing angle can be arbitrarily controlled.

Further, the explanation heretofore has been given of the case of usingthe transparent beads each in a very small spherical shape as amicro-lens. However, the shape of the very small condensing lens is notlimited to that of spherical bodies such as a hemisphere, an ellipsoidof revolution, a circular cylinder, a semicircular cylinder, and anelliptic cylinder so far as the condensing lens is a very small bodyhaving condensing action. That is, the light distribution controlelement according to the present invention is constituted ofmicro-lenses having condensing action and a transparent base membersupporting the micro-lenses, and the transparent base member arranged onthe light emitting side is constituted of a transparent body which issubstantially isotropic optically to thereby prevent light progressingin the transparent base member at angles different from producingvarious phase differences and eliminates occurrence of the fringepattern (non-uniformity in brightness).

Next, an explanation will be given of a light distribution controlelement according to the present invention in reference to specificembodiments.

[Embodiment 1 of Light Distribution Control Element]

In the present embodiment, the light distribution control element shownin FIG. 1 and FIG. 2 is fabricated as follows. First, one surface of atransparent base member 101 comprising a flat triacetylcellulose (TAC)film having a thickness of 80 μm is coated with a polyester-based hotmelt transparent adhering agent (manufactured by Toyo Boseki) usingtoluene as a solvent by a knife coater such that a thickness afterdrying becomes 4 μm, followed by drying in a desiccator and cooling, tothereby form and solidify a transparent adhering agent layer 102.

Next, a colored adhering agent produced by blending the polyester-basedhot melt adhering agent with 10 parts by weight of carbon black isformed and solidified by a method similar to that of the adhering agentlayer 102 such that a thickness after drying becomes 5.5 μm, therebyforming a colored adhering agent layer 103.

Next, a plurality of spherical transparent beads 105 made of glasshaving a refractive index of 1.935 (wavelength: 589.3 nm) and a diameterof 50 μm are arranged to disperse on the colored adhering agent layer103 such that a substantially maximum packing density is achieved, andheld in a thermostatic chamber at 120° C. for 20 minutes while pressingthe beads toward the transparent base member 101 under pressure of 4.5kg/cm² by using a pressing plate. Thereafter, by cooling the resultantlayer to normal temperature, the transparent adhering agent layer 102and the colored adhering agent layer 103 are solidified and thetransparent beads 105 are fixed. The thickness of the hot melt adheringagent layer 104 after fixing the transparent beads is about 21 μm and58% of the diameter of the transparent beads 105 is exposed.

Further, the TAC film used for the transparent base member 101 is atransparent film which is substantially isotropic optically such that(ne-no)=0.0001, (nz-no)=0.0007.

When unpolarized light is made incident on the above-described lightdistribution control element to thereby evaluate the element, there isprovided an isotropic and wide viewing angle (in this case, an angle atwhich brightness becomes a half of brightness in a forward direction) ofabout 60 degree both in the horizontal direction and the verticaldirection.

Further, when linearly polarized light is made to be incident thereon,non-uniformity of brightness causing a fringe pattern is not recognizedand there is provided bright and wide viewing angle characteristics evenviewed at any angle by an observer.

FIG. 9 is an equi-brightness diagram showing light emittingcharacteristics of the light distribution control element in theembodiment when linearly polarized light is made incident thereon, andFIG. 10 shows light emitting (light distributing) characteristics in thehorizontal direction and the vertical direction of the lightdistribution control element in the embodiment when linearly polarizedlight is made incident thereon.

As shown in FIG. 9 and FIG. 10, the light distribution control elementin the embodiment is provided with polarized light dependency in thelight emitting (light distributing) characteristics and a viewing angle(±75 degree) in a direction in parallel with the oscillation directionof the electric vector of incident linearly polarized light (horizontaldirection in the drawing) becomes wider than a viewing angle (±45degree) in a direction orthogonal thereto. This is because of thefollowing reason.

According to the light distribution control element, most of polarizedlight incident on the transparent beads 105 is condensed whilesubstantially maintaining the polarized state, is diverged, progressesin the transparent base member 101 at various angles, and is emitted. Atthis occasion, the transparent bead 105 is a spherical body, andaccordingly, the angle of refraction becomes isotropic regardless ofpolarized light. However, the energy transmittance differs between ppolarized light and s polarized light on the surface of the transparentbead 105 and on the light emitting side surface of the transparent basemember 101, and therefore in respect of the surface of the transparentbead 105 or the transparent base member 101, the transmittance of the ppolarized light component becomes high, the transmittance of the spolarized light component becomes low, and as a result, the polarizedlight dependency is produced in the light distribution characteristics.

Accordingly, when circularly polarized light is made incident on thelight distribution control element, an isotropic viewing angle is formedsimilarly to the case where unpolarized light is made incident thereon.That is, as in the light distribution control element, when as amicro-lens, there is used a revolutionarily symmetric micro-lens as inthe spherical transparent bead, the light distribution characteristicscan be changed comparatively easily in the state of polarizing incidentlight.

Further, when a light distribution control element is fabricated with aconstitution similar to that of the above-described embodiment exceptthat transparent beads having a refractive index of 1.7 are used and itscharacteristics are investigated by making unpolarized light incidentthereon, brightness in a forward direction becomes 1.8 times as much asthat of the above-described embodiment and the viewing angle becomes±37. That is, according to the light distribution control element, thegain and viewing angle can be changed by changing the refractive indexof transparent beads. That is, by pertinently selecting the refractiveindex of the transparent beads, there can be realized a lightdistribution control element having desired characteristics.

[Embodiment 2 of Light Distribution Control Element]

In the present embodiment, the light distribution control element shownin FIG. 1 and FIG. 2 are fabricated as follows.

A surface of a transparent base member 101 comprising a flatpolycarbonate (PC) film having a thickness of 100 μm formed by a castingprocess (a solution flowing and expanding process) is coated with apolyester-based hot melt transparent adhering agent dispersed in anaqueous medium by a knife coater such that a thickness after dryingbecomes 4 μm, is heated and dried, and thereafter, is cooled, to therebyform and solidify a transparent adhering agent layer 102.

Next, a colored adhering agent layer 103 in which 10 parts by weight ofcarbon black is blended to the polyester-based hot melt adhering agentis formed and solidified thereon similarly to the above-described mannersuch that the thickness after drying becomes 5.5 μm.

Next, on top thereof, spherical transparent beads 105 made of glasshaving a refractive index of 1.935 (wavelength: 589.3 nm) and a diameterof 50 μm are embedded and fixed into a hot melt adhering agent layer 104similarly to Embodiment 1. The thickness of the hot melt adhering agentlayer 104 after being fixed is about 21 μm and 58% of the diameter ofthe transparent beads 105 is exposed. Further, the PC film used for thetransparent base member 101 is a transparent film which is substantiallyisotropic optically of (ne-no)≦0.0001. When circularly polarized lightis made incident on the light distribution control element and theelement is evaluated, there is no non-uniformity in brightness causing afringe pattern, and an isotropic and wide viewing angle of about 60° isachieved. Further, when linearly polarized light is made incidentthereon, there is no non-uniformity of brightness causing a fringepattern, and there are provided light emitting characteristics in whichthe viewing angle in a direction in parallel with the oscillationdirection of the electric vector of the incident linearly polarizedlight is wider than the viewing angle in a direction orthogonal thereto.

[Embodiment 3 of Light Distribution Control Element]

In the present embodiment, the light distribution control element shownin FIG. 1 and FIG. 2 is fabricated as follows.

A surface of a transparent base member 101 comprising a uniaxiallyelongated flat PC film having a thickness of 100 μm which is formed byan extrusion process (a molten extrusion process) is coated with apolyester-based hot melt transparent adhering agent dispersed in anaqueous medium by a knife coater such that a thickness after dryingbecomes 4 μm, and is dried and cooled, to thereby form and solidify atransparent adhering agent layer 102.

Next, a colored adhering agent layer 103 is formed and solidifiedsimilarly to Embodiments 1 and 2, transparent beads 105 are arranged todisperse thereon, and thereafter, the transparent beads are held at 120°C. for 30 minutes while being pressed, and are embedded and fixed into ahot melt adhering agent layer 104. The thickness of the hot meltadhering agent layer 104 after being fixed is about 21 μm, and 58% ofthe diameter of the transparent beads 105 is exposed.

Further, the PC film used for the transparent base material 101 is atransparent film with uniaxial anisotropy having an optical axis in adirection in parallel with the film face of (ne-no)=0.0014.

When linearly polarized light in which the oscillation direction of theelectric vector is parallel with or orthogonal to a retarded phase axisof the transparent base member 101 is made incident on the lightdistribution control element, there is no non-uniformity of brightnesscausing a fringe pattern and there is provided light emittingcharacteristics in which the viewing angle in a direction in parallelwith the oscillation direction of the electric vector of incidentlinearly polarized light is wider than a viewing angle in a directionorthogonal thereto.

Further, according to the light distribution control element, physicalproperties such as tensile strength and initial elastic modulus areimproved by uniaxially elongating the transparent base member, and therecan be provided the sheet-like light distribution control element havingless curling or the like.

[Embodiment 4 of Light Distribution Control Element]

In the present embodiment, the light distribution control element shownin FIG. 1 and FIG. 2 is fabricated as follows.

A surface of a flat transparent base member 101 composed of an alicyclicacrylic resin (trade name “Optlet,” manufactured by Hitachi Kasei Kogyo)having a thickness of 2 mm formed by injection molding is coated with anacrylic-based hot melt transparent adhering agent by a spin coater suchthat the thickness after drying becomes 4 μm, and is dried andthereafter cooled, to thereby form and solidify a transparent adheringagent layer 102.

Next, a colored adhering agent layer 103 in which 10 parts by weight ofcarbon black is blended similarly to the acrylic-based hot melt adheringagent is formed and solidified by a method similar to that of thetransparent adhering agent layer 102 such that the thickness afterdrying the adhering agent becomes 5.5 μm.

Spherical transparent beads 105 made of glass having a refractive indexof 1.935 (wavelength: 589.3 nm) and a diameter of 50 μm are arranged todisperse thereon, the beads are held at 120° C. for 20 minutes whilebeing pressed similarly to the above-described embodiments, and embeddedand fixed into the hot melt adhering agent layer 104. The thickness ofthe hot melt adhering agent layer 104 after being fixed is about 21 μmand 58% of the diameter of the transparent beads 105 is exposed.

Further, the alicyclic acrylic resin used for the transparent basemember 101 is substantially isotropic optically such that(ne-no)=0.0007.

When circularly polarized light is made incident on the lightdistribution control element and the element is evaluated, there is nonon-uniformity of brightness causing a fringe pattern and an isotropicand wide viewing angle of about 50 degree is provided. Further, whenlinearly polarized light is made incident thereon, there is nonon-uniformity of brightness causing a fringe pattern, and there isprovided light emitting characteristics in which the viewing angle in adirection in parallel with the oscillation direction of the electricvector of the incident linearly polarized light is wider than a viewingangle in a direction orthogonal thereto.

Further, according to the light distribution control element of theembodiment, there is a rigidity in the transparent base member 101 perse, and accordingly, the element can be used as a screen of a rearprojection type display apparatus even without reinforcement members orthe like.

Although according to the above-described embodiments, the sphericaltransparent bead is used as the micro-lens, micro-lenses having othershapes may be used. FIG. 34 is a schematic perspective view showing anexample of micro-lenses having other shapes. The constitution is similarto those in the above-described embodiments except that a columnarmicro-transparent rod 3401 is used.

According to the light distribution control element, in respect ofincident light, the converging effect is produced not in a long axialdirection of the micro-transparent rod 3401 but only in the directionorthogonal to the long axial direction, and the wide viewing angle isformed only in such a direction. Also in this case, occurrence of afringe pattern at the time of incidence of polarized light can beavoided by using the transparent base member having small opticalanisotropy.

Further, when light incident on the light distribution control elementis linearly polarized light, when an oscillation direction of thepolarized light is made in parallel with the long axial direction of themicro-transparent rod, the polarized light becomes p polarized light inrespect of an incident face of the micro-transparent rod, andaccordingly, the light distribution control element can be used withhigh transmittance.

In the meantime, although according to the above-described respectiveembodiments, the micro-lens is constituted of a previously formed verysmall body such as a transparent bead or rod, the light distributioncontrol element according to the present invention is not limitedthereto. That is, a number of micro-lenses may be formed in atwo-dimensional array directly on the transparent base member. FIG. 35is a schematic perspective view showing an example of such a lightdistribution control element,

According to the light distribution control element, micro-lenses 3502are molded in a two-dimensional array on a transparent base member 3501which is substantially isotropic optically such as glass, anon-elongated PC film, a TAC film or an injection-molded acrylic resinplate and a light absorbing layer (black matrix) 3503 in black colorhaving opening portions are formed at light converging portions of themicro-lenses 3502.

The light absorbing layer 3503 can be formed by well-known technology,for example, a printing process, a vapor deposition process, aphotolithography process or the like. Further, the micro-lens 3502 canbe formed by well-known technology, for example, a method in which apositive type photoresist is exposed by a pattern and developed tothereby provide a stereoscopic columnar shape, and thereafter, adome-like micro-lens is formed by surface tension in heating andmelting; or a method in which a transparent resin film cured by beingirradiated with a light ray or an electron beam is formed on thetransparent base member 3501 and the resin film is selectivelyirradiated with the light ray or the electron beam to thereby cure thefilm and uncured portion is removed.

In any cases, by using a transparent member which is substantiallyisotropic optically or a transparent member having uniaxial opticalanisotropy for the transparent base member 3501, there can be resolvedthe problem of occurrence of a fringe pattern at the time of theincidence of polarized light.

[Embodiment 1 of Rear Projection Type Display Apparatus]

Next, an explanation will be given of a rear projection type displayapparatus using the light distribution control element according to thepresent invention. FIG. 11 is a schematic sectional view of the rearprojection type display apparatus.

According to the projection type display apparatus of the presentinvention, as shown in FIG. 11, a transmission type screen 703 isirradiated with a projected light beam 704 from a projecting apparatus701 via a mirror 702. As the mirror 702, there is used opticallyisotropic, transparent glass vapor-deposited with a reflective metal ofsilver, aluminum or the like.

As the projecting apparatus 701, a so-called liquid crystal projectorcan be used.

FIG. 12 is a schematic sectional view showing an example of the liquidcrystal projector.

A light source 801 is constituted of a reflector having hyperboloid ofrevolution or ellipsoid of revolution and a white color light source ofa Xenon lamp, a metal halide lamp, a halogen lamp or the like, and lightemitted therefrom transmits through an UV and IR cut filter (notillustrated) or the like, to thereby constitute white color lightwithout any ultraviolet ray or infrared ray, and progresses toward acolor separating dichroic mirror 802.

The white color light incident on the color separating dichroic mirror802 is separated into blue color light (B) and other light, and the bluelight (B) is reflected by a total reflection mirror 804 and reaches aliquid crystal display element 807.

In the meantime, green color light (G) and red color light (R) reflectedby the color separating dichroic mirror 802 are separated by a colorseparating dichroic mirror 803, the green color light (G) progressestoward a liquid crystal display element 809. Further, the red colorlight (R) is reflected by total reflection mirrors 805 and 806 andreaches a liquid crystal element 808. TN liquid crystal display elementscan be used for the liquid crystal display elements 807, 808 and 809.

FIG. 13 is a schematic sectional view showing an example of a TN liquidcrystal display element. The liquid crystal display element includes atransparent electrode 903 comprising ITO (Indium Tin Oxide), a firsttransparent glass substrate 901 having an orientation film 905 composedof a polyimide-based polymer, an orientation film 906, a transparentelectrode 904 forming pixels, a second transparent glass substrate 902connected thereto and having wirings, not illustrated, switchingelements of thin film transistors or the like and a liquid crystal layer907 comprising nematic liquid crystals having positive dielectricanisotropy which are enclosed between two sheets of the transparentglass substrates 901 and 902 adhering to each other via a sealing agent908.

The long axial direction of liquid crystal molecules of the liquidcrystal layer 907 is twisted continuously by 90 degree between thetransparent glass substrates by rectifying the orientation direction bysubjecting orientation films 905 and 906 formed on two sheets oftransparent glass substrates 901 and 902 to a rubbing process.

A light incident face and a light emitting face of the liquid crystaldisplay element are respectively provided with a polarizer 909 and ananalyzer 910 to transmit two pieces of linearly polarized lightorthogonal to each other and orientation directions of the long axes ofthe liquid crystal molecules of the liquid crystal layer 907 at thetransparent glass substrates 901 and 902 are respectively constituted tobe parallel with or orthogonal to the transmission axes of the linearlypolarized light at the polarizer 909 and the analyzer 910.

There are used the polarizer 909 and the analyzer 910 having aconstitution in which triacetylcellulose (TAC) protective layers areprovided on both faces of a film provided with a light polarizingfunction by making elongated polyvinyl alcohol (PVA) absorb iodine andthe polarizer and the analyzer are optically coupled to the transparentglass substrate 901 and the transparent glass substrate 902 by anacrylic-based adhering agent.

An explanation will be given here of operation of the liquid crystaldisplay element. Linearly polarized light incident on the liquid crystaldisplay element and transmitted through the polarizer 909, transmitsthrough the liquid crystal layer 907 and is incident on the analyzer910. At this occasion, the polarized state of light transmitting throughthe liquid crystal layer 907 is changed by an electric field applied tothe liquid crystal layer 907, and accordingly, a voltage correspondingto image information is applied to the transparent electrode 905 and thetransparent electrode 904, and the electric field is applied to theliquid crystal layer 907 to thereby achieve the formation of an opticalimage by controlling an amount of light transmitting through theanalyzer 910.

Therefore, the lights of colors respectively incident on liquid crystaldisplay elements 807, 808 and 809 in FIG. 12, are spatially modulatedand emitted in accordance with respective image information. The lightsof colors modulated respectively by the liquid crystal display elementstransmit through polarized state aligning means 812, 813 and 814,described later in details, are incident on a color synthesizing crossdichroic prism 811 and synthesized, and thereafter projected to thetransmission type screen 703 via a projecting lens 810.

FIG. 14 is a schematic sectional view of the transmission type screen703 of the rear projection type display apparatus according to thepresent invention.

The transmission type screen 703 is constituted of a Fresnel lens sheet801 f and the light distribution control element 100 according to thepresent invention. The Fresnel lens 801 f is an optical part operatingsimilarly to a convex lens and operates to collimate diverging projectedlight beam emitted from the projecting apparatus 701 and convert anangle of incidence of light incident on the light distribution controlelement 100 to 0 degree or its approximation.

Here, the light distribution control element 100 according to thepresent invention is provided with a property in which when the angle ofincidence is increased, the transmittance is reduced in view of theconstitution. FIG. 15 is a schematic view for explaining a reduction inthe transmittance based on an increase in angle of incidence.

When the angle θ of incidence of light is increased, the incident light106 is converged by the transparent bead 105 and is emitted from thetransparent base member 101 while being diverged and in such a case, theangle of incidence on the interface between the transparent base member101 and air is increased, and accordingly, reflection is increased andthe transmittance is significantly reduced. Further, when the angle θ ofincidence is further increased, light which is incident on and convergedto the transparent bead 105 cannot transmit through an opening portionof the light distribution control element 100, that is, a portionthereof where the transparent bead 105 is brought into contact with thetransparent adhering agent layer 102 and is absorbed by the coloredadhering agent layer 103 to thereby reduce the transmittance.

FIG. 16 is a graph showing an example of a relationship between theangle of incidence and the transmittance of light of the lightdistribution control element 100. The abscissa designates the angle θ ofincidence of light and the ordinate designates relative transmittanceassuming that the transmittance is 1 when the angle θ of incidence is 0.

When the angle θ of incidence exceeds 10 degree, the transmittance israpidly reduced. Accordingly, it is preferable that the divergence oflight incident on the light distribution control element 100 should besmaller, the better and it is practically preferable to set the angle ofincidence within 10 degree at a half value angle.

Accordingly, when the light distribution control element is used in atransmission type screen of a rear projection type display apparatususing a conventional 3-tube type projecting apparatus using three CRTprojection tubes corresponding to, for example, three primary colors ofR, G and B, the angles of incidence of respective color lights incidenton the color distribution control element differ from each other, andaccordingly, there poses a problem that transmittances of respectivecolor lights differ from each other, white balance is deteriorated orstrong color shift emerges.

Therefore, the rear projection type display apparatus according to thepresent invention is featured in using a projecting apparatus of asingle tube type as a projecting apparatus. In the case of the singletube type, angles of incidence of respective color lights on atransmission type screen coincide with each other, and accordingly, nodeterioration occurs in the white balance or emergence of the colorshift.

Further, the Fresnel lens 801 f is arranged on the light incident sideof the light distribution control element 100 constituting thetransmission type screen 703, the diverging projected light beam 704from the projecting apparatus 701 is collimated and the angle ofincidence of light incident on the light distribution control element100 is converted substantially into 0 degree, to thereby restrain thetransmittance of the color distribution control element 100 fromreducing and promote the brightness of a displayed image.

In this case, according to the TN liquid crystal display element used asa two-dimensional switch element of the projecting apparatus 701,generally, in order to ensure symmetry of the contrast ratio in thehorizontal direction, the element is arranged such that the transmissionaxes of linearly polarized light of the polarizer 909 and the analyzer910 form an angle or 45 degree or 135 degree relative to the horizontaldirection of the display face of the liquid crystal display element. Inthis case, when there are used liquid crystal display elements havingthe same constitution as those of the liquid crystal display elements807, 808 and 809, with respect to image light which have transmittedthrough the liquid crystal display elements, the oscillation directionof an electric vector of linearly polarized light (hereinafter, referredto as the oscillation direction of linearly polarized light) differsbetween image light which is reflected once at the color synthesizingcross dichroic prism 811 and image light which is not reflected at allat the color synthesizing cross dichroic prism 811.

That is, although the red color light (R) and the blue color light (B)which have transmitted through the liquid crystal display element 807and 808 are respectively reflected once at the color synthesizing crossdichroic prism 811, and accordingly, the oscillation directions oflinearly polarized light are the same as each other. However, the greenlight (G) which has transmitted through the liquid crystal displayelement 809 is not reflected at all at the color synthesizing crossdichroic prism 811, and accordingly, the oscillation direction oflinearly polarized light is orthogonal to the oscillation direction oflinearly polarized light of the other color lights.

As described above, the light emitting characteristics of the lightdistribution control element 100 according to the present invention arechanged depending on the polarized state of the incident light.Therefore, when the light distribution control element according to thepresent invention is used as the transmission type screen of theconventional rear projection type display apparatus, when observed in acertain direction, an image exhibits a green color, further, whenobserved in the oblique direction inverse thereto, the image exhibits amagenta color.

In order to correct these, the rear projection type display apparatus701 according to the present invention is featured in arranging thepolarized state aligning means 812, 813 and 814 on the light emittingsides of the liquid crystal display elements 807, 808 and 809.

The polarized state aligning means 812, 813 and 814 are provided with afunction for making the polarized states of the respective color lightscoincide with each other before the respective color lights emitted fromthe liquid crystal display elements are projected on the transmissiontype screen 703.

FIG. 17 is a schematic sectional view showing an example of thepolarized state aligning means. The polarized state aligning means isconstituted of a transparent substrate 1001 formed of a polyimide-basedorientation film 1003, a transparent substrate 1002 formed of apolyimide-based orientation film 1004 and a liquid crystal layer 1006comprising nematic liquid crystals enclosed between two transparentsubstrates. A clearance is defined between the two transparentsubstrates 1001 and 1002 via a spacer, not illustrated. The twotransparent substrates adhere to each other by sealing the surroundingsby a sealing agent 1005, and liquid crystals are hermetically sealed.

FIG. 18 illustrates operation of the polarized state aligning means. Forthe sake of easy understanding, the orientation directions of long axesof liquid crystal molecules in the vicinity of the transparentsubstrates of the liquid crystal display element as well as thepolarized state aligning are indicated by arrows 911, 912, 1007 and1008, respectively.

As exemplified in FIG. 18, according to the liquid crystal layer 1006 ofthe polarized state aligning means, by orientation films on the twotransparent substrates 1001 and 1002, the long axes of liquid crystalmolecules are twisted by 45 degree between the two transparentsubstrates and the liquid crystal orientation direction 1008 on the sideof the transparent substrate 1001 is oriented in the horizontaldirection relative to a display face of the liquid crystal displayelement.

On the other hand, the liquid crystal orientation direction 1007 on theside of the transparent substrate 1002 on the side of the liquid crystaldisplay element, is parallel with the liquid crystal orientationdirection 912 of the transparent substrate 910 on the light emittingside of the liquid crystal display element and is inclined by 45 degreeto the horizontal direction of the display face of the liquid crystaldisplay element.

The polarized state aligning means is constituted to satisfy thecondition of a waveguide in respect of a main wavelength region ofincident light. The condition of the waveguide is described in a paperby C. H. Gooch and H. A. Tarry “J. Phys. D: Appl. Phys. Vol. 8 (1975),pp. 1575-1584.”

That is, in order to subject light having a wavelength λ to rotarypolarization by a waveguide, birefringence Δn of the liquid crystallayer 1006 of the polarized state aligning means at a layer thickness dand the wavelength λ may be set to satisfy Equation (1) shown below.4d·Δn/λ=V(4m ²−1)  (1)

where m represents an arbitrary integer.

Accordingly, d and Δ n of the polarized state aligning means 812, 813and 814 may be set to satisfy Equation (1) in respect of a mainwavelength of light incident thereon, in this case, the main wavelengthsof light incident on the polarized state aligning means 812, 813 and 814are respectively set to 450 nm, 650 nm and 550 nm and m is set to 4, andd·Δn is set to 626 nm, 903 nm and 765 nm, respectively.

Further, the condition of the waveguide does not differ between anextraordinary wave mode and an ordinary wave mode, and accordingly, withregard to the orientation direction of the liquid crystal of thepolarized state aligning means, the orientation directions of the twotransparent substrates may be rotated by 90 degree relative to theorientation directions exemplified in FIG. 18.

By constituting in this way, when linearly polarized lights which havetransmitted through the liquid crystal elements 807, 808 and 809transmit through the polarized state aligning means 812, 813 and 814,the oscillation directions of electric vectors thereof are rotated by 45degree to thereby constitute linearly polarized lights having theoscillation directions horizontal to the display faces of the liquidcrystal display elements by which all of the polarized states of therespective color lights coincide with each other.

Further, the effect below is achieved by directing the oscillationdirections of the linearly polarized lights of the respective colorlights in the horizontal direction relative to the display faces, likein the present embodiment.

Generally, in a single tube type of a projecting apparatus using aplurality of two-dimensional optical switch elements, in order tosynthesize optical image lights formed by the respective two-dimensionaloptical switch elements, a cross dichroic prism or a dichroic mirror isused.

A reflecting face of the dichroic prism or the dichroic mirror is formedby a multiple-layered film of a dielectric body, a polarized state oflinearly polarized light obliquely incident thereon is changed inreflection in the case other than p polarized light in parallel with anincident face or s polarized light orthogonal to the incident face, andgenerally, an elliptically polarized light is constituted and thepolarized state differs among respective color lights. However, asdescribed above, when oscillation directions of pieces of linearlypolarized light of respective pieces of color light are incident on adisplay face in the horizontal direction, that is, as the p polarizedlight in respect of a reflecting face of the color synthesizing dichroicprism, polarized states of the respective pieces of color light are notchanged, and optical image light can be projected to the transmissiontype screen while the polarized states of all of the color lightscoincide with each other.

That is, according to the back-face display apparatus of the presentinvention, the polarized states of the respective color lights projectedfrom the projecting apparatus 701 coincide with each other, andaccordingly, there is achieved an effect in which staining caused by thedependency of the light distribution characteristics on polarized lightin the light distribution control element 100 used as the transmissiontype screen 703 is resolved and image of high grade can be provided.

Further, projected light incident on the transmission type screen 701 isthe linearly polarized light having the oscillation direction in thehorizontal direction relative to the display face, and accordingly, bythe polarized light dependency of the light distribution characteristicsin the light distribution control element 100, the viewing angle in thehorizontal direction can be made wider than that in the verticaldirection. This is very effective in view of distributing efficientlylimited light to an observer since generally in a display apparatus aviewing angle in the horizontal direction is requested to be wider thanthat in the vertical direction.

When the rear projection type display apparatus having theabove-described constitution is evaluated by using the lightdistribution control element 100 of the transmission type screen 703 inwhich a surface of the light distribution control element 100 on theside of the transparent base member 101 exemplified in Embodiment 1 oflight distribution control element, is clad with an acrylic plate havinga thickness of 2 mm, which is flat, transparent and substantiallyisotropic optically, wide viewing angles are provided both in twodirections such as a viewing angle of about 75 degree in the horizontaldirection and a viewing angle of about 45 degree in the verticaldirection. Further, when observed in an oblique direction, no fringepattern or staining is caused.

Further, unnecessary light incident on the transmission type screen fromoutside is absorbed by the colored adhering agent layer 103 of the lightdistribution control element 100, and accordingly, there is realizedblack display having a brightness as low as 0.5 cd/m² under a brightenvironment (vertical brightness: 3001x).

Further, according to the polarized state aligning means of the rearprojection type display apparatus of the present invention, any meanscan be used so far as the means is provided with a function of makingpolarized states of color lights emitted from liquid crystal displayelements coincide with each other, other than the means in theabove-described embodiments, there can be used, for example, a polymerlaminated layer film or a half wave plate having a twist structure.

The polymer laminated layer film having the twist structure used as thepolarized state aligning means is realized by laminating, for example,four sheets of phase difference films made of PC films having a phasedifference d·Δn=275 nm. The four sheets of phase difference films arearranged such that respective retarded phase axes thereof constitute 5.6degree, 16.9 degree, 28.1 degree and 39.4 degree relative to a liquidcrystal orientation direction of a transparent substrate on the lightemitting side of a liquid crystal element from one of the filmsproximate to the liquid crystal display element. Also in this case, aneffect similar to that in the above-described embodiments is achieved.

When a half wave plate is used as the polarized state aligning means, aneffect similar to that in the above-described embodiments is achieved byarranging the half wave plate such that a retarded phase axis of thewave plate functioning as the half wave plate with regard to awavelength of light which are transmitted through the respective liquidcrystal display element, is inclined by 22.5 degree relative to atransmission axis of an analyzer of the liquid crystal display element.

Further, staining in observing in an oblique direction can be preventedto a certain degree by arranging the half wave plate as the polarizedstate aligning means only on the light emitting side of a liquid crystaldisplay element which differs from other to thereby make an oscillationdirection of emitted linearly polarized beam coincide with that in apolarized state of the other liquid crystal display element.

Further, although according to the above-described embodiments, anexplanation has been given of the case where the transmission axis ofthe linearly polarized light of the analyzer of the liquid crystaldisplay apparatus is inclined by 45 degree relative to the horizontaldirection of the display face, for example, by using a liquid crystaldisplay element previously constituted such that a transmission axis ofan analyzer is directed in the horizontal direction or the verticaldirection relative to the display face, the liquid crystal displayelement can also be provided with the function of the polarized statealigning means. In this case, the polarized states of color lightsemitted from liquid crystal display elements coincide with each othereven after synthesizing the colors, and accordingly, an effect similarto those in the above-described embodiments can be achieved withoutarranging other optical elements on the light emitting side of theliquid crystal display elements.

However, in this case, the symmetry of the contrast ratio in thehorizontal direction is deteriorated, and accordingly, a projectionoptical system having a high F value may be used such that lateralnon-symmetry of the contrast ratio cannot be recognized.

As described above, according to the rear projection type displayapparatus of the present invention, the transmission type screen 703 isconstituted of the light distribution control element 100 and theFresnel lens 801 f arranged on the light incident side. Therefore, thediverging projected light 704 from the projecting apparatus 701 iscollimated by the Fresnel lens 801 f when the light is incident on thelight distribution control element 100 and the angle of incidence issubstantially converted into 0 degree, and accordingly, thetransmittance at the light distribution control element 100 isrestrained from being reduced and a bright display image is provided.

Further, according to the present invention, by using a single tube typeprojecting apparatus as the projecting apparatus, color shift orstaining produced by the optical characteristics of the lightdistribution control element 100 can be restrained and a high gradeimage can be provided.

Further, by making the polarized states of emitted light from theprojecting apparatus coincide with each other in the color lights, thereis achieved an effect of capable of eliminating staining produced whenobserved in an oblique direction, which is produced by the polarizedlight dependency of the light distribution characteristics of the lightdistribution control element 100. Further, the light distributioncontrol element 100 according to the present invention used as thetransmission type screen 703 is provided with characteristics of a wideviewing angle which is bright as viewed at any angle and is providedwith a high effect of reducing stray light produced by outsideunnecessary light, and accordingly, there is achieved an effect capableof realizing the rear projection type display apparatus achieving a wideviewing angle as well as a high contrast ratio by realizing blackdisplay having a low brightness even under a bright environment.

Further, although according to the above-described rear projection typedisplay apparatus, the explanation has been given of the case where theplurality of two-dimensional optical switch elements are used in theprojecting apparatus, there may be used a projecting apparatus of aso-called single plate type in which only one of the two-dimensionaloptical switch elements is used. In this case, since there is only oneof the two-dimensional optical switch element inherently, and therefore,a polarized state of optical image light is uniquely determined withoutany aligning, and accordingly, staining is not produced by the polarizedlight dependency of the light distribution characteristics of the lightdistribution control element 100 according to the present invention.

[Embodiment 2 of Rear Projection Type Display Apparatus]

Next, an explanation will be given of another rear projection typedisplay apparatus according to the present invention. Similarly to theabove-described embodiment explained in reference to FIG. 11, the rearprojection type display apparatus, described here, is provided with theprojecting apparatus 701, the mirror 702 and the transmission typescreen 703, the transmission type screen 703 is irradiated with theprojected light beam 704 emitted from the projecting apparatus 701 viathe mirror 702 to thereby display an image; however, the constitution ofthe projecting apparatus 701 differs therefrom partially.

FIG. 19 is a schematic sectional view of a projecting apparatusaccording to a rear projection type display apparatus in the presentembodiment.

Although the projecting apparatus is basically similar to the projectingapparatus exemplified in FIG. 12, the projecting apparatus 701,described here, is featured in arranging a polarized state convertingelement 815 between the projecting lens 801 and the cross dichroic prism811.

According to the projecting apparatus, similarly to the above-describedembodiment, white color light emitted from the light source 801 isseparated into blue color light (B), green color light (G) and red colorlight (R) by the color separating dichroic mirrors 802 and 803, and theseparated color lights are respectively incident on the liquid crystaldisplay elements 807, 809 and 808 via the mirrors 804, 805 and 806. Thelights incident on the liquid crystal display elements are spatiallymodulated in accordance with image information of the respective colorsand emitted, and the color lights become linearly polarized lightshaving a coincident oscillation direction by the polarized statealigning means 812, 813 and 814 and are incident on the colorsynthesizing cross dichroic prism 811.

In this case, it is preferable that the respective colors of lightsincident on the color synthesizing cross dichroic prism 811 areconstituted of p polarized light or s polarized light with regard to themirror face of the prism 811. Because the mirror face of the colorsynthesizing prism 811 is constituted of a multiple-layered film of adielectric body. Unless special design or film formation is carried out,when linearly polarized light obliquely incident on the mirror face isnot p polarized light in parallel with the incident face or s polarizedlight orthogonal to the incident face, the polarized state is changed inreflection. Generally, an elliptically polarized light is constitutedand the polarized states of the respective colors of pieces of lightbecome different from each other.

An explanation will be given here of an example in the case where imagelight is incident on the prism 811 as p polarized light relative to themirror face of the color synthesizing cross dichroic prism 811, that is,as linearly polarized light having an oscillation direction in thehorizontal direction relative to the display face as follows.

The image light incident on and color-synthesized by the colorsynthesizing dichroic prism 811 is projected to the transmission typescreen 703 via the polarized state converting element 815 and theprojecting lens 810.

The polarized state converting element 815 changes a polarized state ofthe image light after color-synthesizing and a liquid crystal elementshown in, for example, FIG. 20 can be used therefor. The polarized stateconverting element 815 shown in FIG. 20 is constituted of a firsttransparent glass substrate 1101 laminated with a transparent electrode1103 composed of ITO and an orientation film 1104 composed of apolyimide-based polymer over the entire face thereof, a secondtransparent glass substrate 1102 similarly laminated with a transparentelectrode 1105 and an orientation film 1106 over the entire face thereofand a liquid crystal layer 1107 defining a clearance between two glasssubstrates 1101 and 1102 via a spacer, not illustrated, and comprisingnematic liquid crystals having a positive dielectric anisotropy whichare enclosed in a space defined by sealing the surroundings with asealing agent 1108.

There are constituted a so-called TN liquid crystal element in which thelong axes of liquid crystal molecules of the liquid crystal layer 1107are continuously twisted by 90 degree between the two substrates bycarrying out orientation processing such as rubbing processing on theorientation films 1104 and 1106 respectively formed at the two sheets oftransparent glass substrates 1101 and 1102.

Next, an explanation will be given of operation of the polarized stateconverting element 815 in reference to the drawings. FIG. 21 and FIG. 22are schematic views for explaining operation of the polarized stateconverting element 815 and arrows 1110 and 1111 respectively indicateorientation directions of liquid crystals at the transparent glasssubstrates 1101 and 1102.

The orientation direction 1111 of the liquid crystals at the transparentglass substrate 1102 on the light incident side is parallel with (ororthogonal to) the oscillation direction of the electric vector ofincident and linearly polarized light., and the liquid crystal layer1107 satisfies the condition of a waveguide in a visible wavelengthregion.

Therefore, when an electric field is not applied to the liquid crystallayer 1107 of the polarized state converting element 815, as exemplifiedin FIG. 21, optical image light incident on the polarized stateconverting element 815 becomes linearly polarized light in which theoscillation direction of the electric vector is rotated by 90 degree,that is, linearly polarized light having the oscillation direction inthe vertical direction relative to the display face and is projected onthe transmission type screen 703 via the projecting lens 810.

Similarly to the above-described embodiment, the transmission typescreen 703 used in the back-face projection display apparatus isconstituted of a light distribution control element using sphericaltransparent beads as micro-lenses and a Fresnel lens.

In this case, as described above, when projected light incident on thetransmission type screen 703 is linearly polarized light having theoscillation direction in the vertical direction relative to the displayface, by the polarized light dependency of the light distributioncharacteristics of the light distribution control element 100, theviewing angle in the vertical direction becomes wider than that in thehorizontal direction.

Further, as exemplified in FIG. 22, when molecular long axes of liquidcrystal molecules are made substantially orthogonal to the transparentglass substrates by applying a voltage across the transparent electrode1103 and the transparent electrode 1105 formed on the two sheets oftransparent glass substrates and applying an electric field to theliquid crystal layer 1107, optical image light incident on the polarizedstate converting element 815 transmits therethrough without almost anychange in the polarized state. That is, the linearly polarized lighthaving the oscillation direction in the horizontal direction relative tothe display face is projected as it is to the transmission type screen703 via the projecting lens 810. In this case, by the polarized lightdependency of the light distribution characteristics of the lightdistribution control element 100 constituting the transmission typescreen 703, the viewing angle in the horizontal direction becomes widerthan that in the vertical direction.

That is, although according to the conventional rear projection typedisplay apparatus, the viewing angle characteristics cannot be changedunless the transmission type screen is replaced, according to the rearprojection type display apparatus of the present invention, there isachieved an epoch-making effect in which the viewing anglecharacteristics can be easily changed by a simple operation ofcontrolling the electric field applied to the liquid crystal layer ofthe polarized state converting element 815.

Further, an ECB (Electrically Controlled Birefringence) liquid crystalelement can be used for the polarized state converting element 815 ofthe rear projection type display apparatus according to the presentinvention other than the above-described TN liquid crystal element. Inthis case, a difference from the TN liquid crystal element is only aportion related to the liquid crystal layer such as the thickness of theliquid crystal layer or the orientation direction of liquid crystalmolecules. Therefore, an explanation will be given of the schematicsectional view of the TN liquid crystal element exemplified in FIG. 20.

Similarly to the polarized state converting element 815 constituted ofthe above-described TN liquid crystal element, the polarized stateconverting element 815 constituted of the ECB liquid crystal element isconstituted of the first transparent glass substrate 1101 laminated withthe transparent electrode 1103 composed of ITO and the orientation film1104 composed of a polyimide-based polymer over the entire face, thesecond transparent glass substrate 1102 similarly laminated with thetransparent electrode 1105 and the orientation film 1106 over the entireface and the liquid crystal layer 1107 defining the clearance betweenthe two sheets of transparent glass substrates via a spacer, notillustrated, and comprising nematic liquid crystals enclosed in thespace defined by connecting the surroundings by the sealing agent 1108.

Although the dielectric anisotropy of nematic liquid crystals may bepositive or negative, the orientation of liquid crystals is set tohomogeneous orientation in the case of nematic liquid crystals havingpositive dielectric anisotropy or to homeotropic orientation in the caseof nematic liquid crystals having negative dielectric anisotropy.

In this case, in order to align the orientation direction of liquidcrystals when an electric field is applied to the liquid crystal layer1107, in either of the cases, a pretilt angle of about 1 through 4degree is formed and the orientation processing is carried out such thata direction of molecular long axes of liquid crystals becomes adirection of 45 degree relative to the display face.

When the thickness of the liquid crystal layer 1107 is represented by dand refractive index anisotropy of liquid crystals are represented by n,d·Δn is set to be equal to or larger than λ/2 (λ is central wavelengthsof optical image light).

According to the polarized state converting element 815 constituted inthis way, by applying a voltage across the transparent electrodes 1103and 1105 formed on the two sheets of transparent glass substrates andapplying an electric field to the liquid crystal layer 1107, an apparentvalue d·Δn of the liquid crystal layer 1107 can be controlled in a rangeof 0 through λ/2 relative to incident optical image light.

Therefore, when the apparent value of d·Δn of the liquid crystal layer1107 is 0, optical image light incident on the polarized stateconverting element 815 transmits therethrough without almost any changeof the polarized state, and accordingly, the optical image light isincident on the transmission type screen 703 as linearly polarized lighthaving the oscillation direction in the horizontal direction relative tothe display face. In this case, by the polarized light dependency of thelight distribution characteristics of the light distribution controlelement 100 constituting the transmission type screen 703, the viewingangle in the horizontal direction becomes wider than that in thevertical direction.

Further, when the apparent value of d·Δn of the liquid crystal layer isλ/2, image light incident on the polarized state converting element 815becomes linearly polarized light in which the oscillation direction ofthe electric vector is rotated by 90 degree, that is, linearly polarizedlight having the oscillation direction in the vertical directionrelative to the display face and is incident on the transmission typescreen 703. In this case, by the polarized light dependency of the lightdistribution characteristics of the light distribution control element100, the viewing angle in the vertical direction becomes wider than thatin the horizontal direction.

Further, when the apparent value of d·Δn of the liquid crystal layer isλ/4, image light incident on the polarized state converting element 815substantially becomes circularly polarized light and is incident on thetransmission type screen 703. In this case, there is provided anisotropic viewing angle having the same degree both in the verticaldirection and the horizontal direction.

Here, a specific explanation will be given of operation of the polarizedstate converting element 815 constituted of the ECB liquid crystalelement in reference to FIG. 23 and FIG. 24.

There are used nematic liquid crystals having a dielectric anisotropy ofΔε=−4.2 and a refractive index anisotropy of Δn=0.083 as liquid crystalsof the polarized state converting elements 815 and a thickness of theliquid crystal layer is set to 3.5 μm.

Polyimide-based orientation films showing vertical orientationperformance are used for the orientation films 1104 and 1105, rubbingprocessing is carried out in a direction constituting an angle of 45degree relative to the horizontal direction of the display face andabout 2 degree of pretilt is provided to liquid crystal molecules.

According to the liquid crystal layer 1107 of the polarized stateconverting element 815, in the case of applying no electric field, theapparent value of d·Δn of the liquid crystal layer 1107 is substantiallynull, as shown in FIG. 23, incident optical image light transmitstherethrough without almost any change in the polarized state and isprojected to the transmission type screen 703 via the projecting lens810 in a state of linearly polarized light having the oscillationdirection in the horizontal direction relative to the display face. Inthis case, by the polarized light dependency of the light distributioncharacteristics of the light distribution control element 100constituting the transmission type screen 703, the viewing angle in thehorizontal direction becomes wider than that in the vertical direction.

On the other hand, as shown in FIG. 24, when molecular long axes ofliquid crystal molecules are inclined from the vertical direction to thehorizontal direction relative to the transparent glass substrates byapplying a voltage across the transparent electrodes formed on twosheets of the transparent glass substrates and by applying an electricfield to the liquid crystal layer 1107 such that the apparent value ofd·Δn of the liquid crystal layer 1107 becomes 225 nm, image lightincident on the polarized state converting element 815 becomes linearlypolarized light having the oscillation direction in the verticaldirection relative to the display face by rotating the oscillationdirection of the electric vector substantially by 90 degree, or anelliptically polarized light having a long axis in a directionsubstantially orthogonal to the display face and is incident on thetransmission type screen 703. In this case, by the polarized lightdependency of the light distribution characteristics of the lightdistribution control element 100 constituting the transmission typescreen 703, the viewing angle in the vertical direction becomes widerthan that in the horizontal direction.

Further, when by applying a voltage to the transparent electrodes formedon the two sheets of transparent glass substrates of the polarized stateconverting element 815 and applying an electric field to the liquidcrystal layer 1107, molecular long axes of liquid crystal molecules areinclined from the vertical direction to the horizontal directionrelative to the transparent glass substrates and the apparent value d·Δnof the liquid crystal layer is changed to 137.5 nm, optical image lightincident on the polarized state converting element 815 becomessubstantially circularly polarized light and is incident on thetransmission type screen 703. In this case, an isotropic viewing anglehaving the same degree both in the horizontal direction and the verticaldirection is provided by the characteristic of the light distributioncontrol element 100 constituting the transmission type screen 703.

That is, although according to the conventional rear projection typedisplay apparatus, unless the transmission type screen is replaced, theviewing angle characteristics cannot be changed, according to the rearprojection type display apparatus, by controlling the electric fieldapplied to the liquid crystal layer of the polarized state convertingelement 815 constituted of the TN liquid crystal element or the ECBliquid crystal element, the viewing angle characteristics can be easilychanged such that the viewing angle in the horizontal direction iswidened, the viewing angle in the vertical direction is widened or theisotropic viewing angle having the same degree both in the horizontaldirection and the vertical direction is provided.

Further, although the description has been made on the case where theviewing angle characteristics are made variable by using the liquidcrystal element as the polarized light converting element 815, otherthan this, desired viewing angle characteristics may be achieved byarranging, for example, a phase contrast plate as the polarized stateconverting element 815. For example, there are conceivable variousmodifications such that, for example, a quarter wave plate is arrangedas the polarized light converting element 815 and an isotropic viewingangle is provided by making optical image light incident on thetransmission type screen 703 by circularly polarized light.

[Embodiment 3 of Rear Projection Type Display Apparatus]

Next, an explanation will be given of a further rear projection typedisplay apparatus according to the present invention. FIG. 40 is aschematic constitution perspective view of a rear projection typedisplay apparatus in the present embodiment.

The rear projection type display apparatus in the present embodiment isconstituted of the rear projection type display apparatus in Embodiment2, mentioned above, added with an observer sensing unit 4002 for sensingpresence or absence of an observer, observer position determining means(not illustrated) for receiving a sensed signal from the observersensing unit and determining positions of an observer in the horizontaland vertical directions and control signal outputting means (notillustrated) for outputting a control signal to the polarized stateconverting element arranged in the projecting apparatus 701 based on theinformation.

The observer sensing unit 4002 is constituted of a plurality of observersensing sensors. The observer sensing sensors sense the observer presentin a plurality of partitioned regions. An infrared ray sensor is usedfor the observer sensing sensor.

FIG. 41 and FIG. 42 exemplify the partitioned regions sensed by theobserver sensing sensors. FIG. 41 shows the case where the verticaldirection is partitioned in three regions of I, II and III, and FIG. 42shows the case where the horizontal direction is partitioned into threeregions of A, B and C. According to the example, there are needed nineof the observer sensing sensors for sensing the observer 4110.

The nine observer sensing sensors provided at the above-describedobserver sensing unit 4002 sense the observer 4100 observing in front ofa rear projection type display apparatus 4001, and the observer positiondetermining means determines at which region (position) in the verticaland the horizontal directions the observer 4100 is present based on therespective sensed signals. Based on information of the observer positiondetermining means, the control signal outputting means outputs a controlsignal to the polarized state converting element of the projectingapparatus 701.

In this case, similarly to Embodiment 2 described above, the rearprojection type display apparatus in the present embodiment can changethe viewing angle characteristics of the transmission type screen 703 bychanging the polarized state of the projected light beam 704 by thepolarized light converting element in the projecting apparatus 701. Thatis, by sensing and determining the positions of the observer, thepolarized state converting unit is controlled and the polarized state ofthe projected light beam 704 is converted into a pertinent state, tothereby provide bright image to the observer.

Next, an explanation will be given of the effect of the back-faceprojection display apparatus in reference to FIG. 43 and FIG. 44.Generally, according to the rear projection type display apparatus, inorder to effectively distribute limited light in a direction of theobserver, the viewing angle in the vertical direction is set to benarrower than the viewing angle in the horizontal direction. Asexemplified in FIG. 43, over the entire face of the screen 703, aneffective range providing image having the uniform brightness is narrowin the vertical direction. Therefore, the observer 4100 cannot beprovided with an excellent image quality unless the observer is seatedon a chair and observes the image at a suitable height or the observerobserves the image with a constant distance held therebetween.

Accordingly, as exemplified in FIG. 43, there poses a problem thatalthough the observer 4100 can observe an excellent image when theobserver is seated on a chair, the image at the lower portion of thescreen 703 becomes dark and no excellent image can be observed.

However, according to the rear projection type display apparatus, whenthe observer stands up, the observer 4102 who stands up is sensed by theobserver sensing unit 4002 and the position of the observer isdetermined by the observer position determining means based on thesensed signal. Further, by controlling the polarized state convertingelement by the control signal outputting means based on the positioninformation of the observer and converting the polarized state of theprojected light beam into a pertinent state, as exemplified in FIG. 44,an excellent image can be provided to the observer 4102 who stands up byenlarging the viewing angle in the vertical direction.

More specifically, in the state exemplified in FIG. 43, by constitutingthe projected light projected to the screen 703 by linearly polarizedlight having the oscillation direction in the horizontal directionrelative to the display face of the screen 703, the viewing anglecharacteristics have the viewing angle in the horizontal direction widerthan that in the vertical direction.

However, when the observer stands up, by controlling the polarized stateconverting element based on the sensed signal from the observer sensingunit 4002 and converting the projected light beam into linearlypolarized light having the oscillation direction in the verticaldirection relative to the display face of the screen 703, as exemplifiedin FIG. 44, an excellent image can be provided to the observer 4102 bywidening the viewing angle in the vertical direction.

As described above, according to the rear projection type displayapparatus, the viewing angle characteristics are automatically changedin accordance with the positions of the observer and limited image lightcan effectively distributed in the direction of the observer, andaccordingly, the observer can be provided with an excellent image at anarbitrary position.

[Embodiment 4 of Rear Projection Type Display Apparatus]

Next, an explanation will be given of a still further rear projectiontype display apparatus according to the present invention. Although therear projection type display apparatus in the present embodiment issimilar to the above-described embodiments explained in reference toFIG. 11, the constitution of the two-dimensional optical switch elementused in the projecting apparatus 701 differs from each other.

The rear projection type display apparatus is featured in that thetwo-dimensional optical switch element used in the projecting apparatus701 does not use polarized light in display and the display is carriedout in an unpolarized state to thereby constitute a feature of basicallysolving the problem of occurrence of a fringe pattern caused by opticalanisotropy of the transparent base member of the light distributioncontrol element 100 constituting the transmission type screen 703 or achange in chromaticity caused by the polarized light dependency of thelight distribution characteristics of the light distribution controlelement.

Although the two-dimensional optical switch element which does not usepolarized light is variously conceivable, in this case, an explanationwill be given firstly of the case where a polymer dispersion type liquidcrystal element is used as a scattering type display element.

As polymer dispersion type liquid crystal elements, there are an elementin which nematic crystals contained in microcapsules and having positivedielectric anisotropy are dispersed in a polymer, an element in whichliquid crystal droplets are dispersed in a polymer matrix, an element inwhich a polymer in a net mesh shape is formed in a liquid crystalcontinuous layer, and so on.

FIG. 25 is a schematic sectional view showing an example of a polymerdispersion type liquid crystal. The polymer dispersion type liquidcrystal 2500 is constituted of a first transparent glass substrate 2501formed of a transparent electrode 2503 composed of ITO over the entireface thereof, a second transparent glass substrate 2502 having atransparent electrode 2504 forming pixels as well as wirings, notillustrated, switching elements of thin film transistors or the likeconnected thereto, and a polymer dispersing liquid crystal layer 2505formed between two sheets of the transparent glass substrates 2501 and2502 connected to each other via a sealing agent 2508.

The polymer dispersing liquid crystal layer 2505 is dispersed withliquid crystal droplets 2506 having positive dielectric anisotropy in apolymer 2507 of polyvinyl alcohol or the like and a refractive index ina direction of a short axis of a liquid crystal molecule substantiallycoincides with a refractive index of the polymer.

FIG. 26 illustrates operation of the polymer dispersion type liquidcrystal element. When an electric field is not applied to the polymerdispersing liquid crystal layer 2505, liquid crystals of the polymerdispersing liquid layer 2505 are arranged irregularly by undergoinginfluence of anchoring by side walls of a polymer, the shape of a wallface, surface energy or the like. Therefore, in the polymer dispersingliquid crystal layer 2505, small particles having a refractive indexdistribution from a refractive index ne in a direction of a long axis ofthe liquid crystal molecule to a refractive index no in a direction ofthe short axis of the liquid crystal molecule, are floated in thepolymer matrix having a refractive index of no, and incident light isrefracted at interfaces having different refractive indices and isscattered.

In the meantime, when a voltage is applied to the transparent electrodeson the transparent glass substrates 2501 and 2502 and an electric fieldis applied to the liquid crystals, the molecular long axes of the liquidcrystals are arranged in a direction orthogonal to the transparent glasssubstrates, the refractive indices of the liquid crystals viewed in theprogressing direction of light become constant to be no and coincidewith the refractive index of the polymer matrix. Therefore, the incidentlight transmits through the interfaces between the liquid crystals andthe polymer without being scattered.

In this way, according to the polymer dispersion type liquid crystalelement, the degree of scattering of light can be changed by applying ornot applying the electric field to the polymer dispersing liquid crystallayer 2505. However, an amount of transmitting light cannot be changed,and accordingly, there is needed an optical system for converting thedegree of scattering light into brightness of light in order to use thisfor display. As is well known, for such an object, a schlieren opticalsystem is used.

FIG. 27 and FIG. 28 are schematic views for explaining display operationof the polymer dispersion type liquid crystal element using theschlieren optical system. A substantially parallel light ray emittedfrom a light source 2801 is converged to an opening portion of anincident side diaphragm 2803 by operation of a converging lens 2802 andthe light which has transmitted through the opening portion of theincident side diaphragm 2803 is collimated by a lens 2701 into asubstantially parallel ray and is incident on a polymer dispersion typeelement 2500. As illustrated, when a sufficient electric field isapplied to the polymer dispersing liquid crystal layer of the polymerdispersion type liquid crystal element 2500, light incident on thepolymer dispersion type liquid crystal element 2500 transmitstherethrough substantially as the collimated light, is converged by aconverging lens 2702, and transmits through an opening portion of anemitting side diaphragm 2817.

In the meantime, as shown in FIG. 28, when the electric field is notapplied to the polymer dispersing liquid crystal layer of the polymerdispersion type liquid crystal element 2500, light incident on thepolymer dispersion type liquid crystal element 2500 is scattered and canhardly transmit through the opening portion of the emitting sidediaphragm 2817. Therefore, by using light transmitting through theemitting side diaphragm 2817 for display, display of the brightness canbe carried out.

Next, an explanation will be given of a projecting apparatus using thepolymer dispersion type liquid crystal element as the two-dimensionaloptical switch element.

FIG. 29 is a schematic sectional view showing an example of a projectingapparatus using the polymer dispersion type liquid crystal element.

A light source 2801 is constituted of a reflector in a shape ofhyperboloid of revolution and a metal halide lamp provided with a lightemitting unit at a focal position of the reflector, and most of lightemitted from the light emitting unit is reflected by the reflector,substantially collimated and is emitted. Light emitted from the lightsource 2801 becomes white color light without any ultraviolet ray orinfrared ray by transmitting through an UV and IR cut filter (notillustrated) and is converged to the opening portion of the incidentside diaphragm 2803 by operation of the incident side converging lens2802.

According to the white color light which has transmitted through theincident side diaphragm 2803, a red color light component thereof isreflected by a red color reflecting dichroic mirror 2804, and thereflected red color light is incident on an incident side lens 2812 viaa total reflection mirror 2807, is collimated by operation of theincident side lens and is incident on a polymer dispersion type liquidcrystal element 2815.

In the meantime, a green color light component in the light which hastransmitted through the red color light reflecting dichroic mirror 2804,is reflected by a green color light reflecting dichroic mirror 2805, isincident on an incident side lens 2811, is collimated by the operationand is incident on a polymer dispersion type liquid crystal element2814.

Further, blue color light which has transmitted through the green colorlight reflecting dichroic mirror 2805 is incident on an incident sidelens 2810, is collimated by the operation and is incident on a polymerdispersion type liquid crystal element 2813.

The color lights incident on the polymer dispersion type liquid crystalelements 2813, 2814 and 2815 are emitted from the polymer dispersiontype liquid crystal elements such that scattering states thereof arecontrolled in accordance with image information. The red color lightwhich has transmitted through the polymer dispersion type liquid crystalelement 2815 is incident on a projecting lens 2819 by transmittingthrough a green color light reflecting dichroic mirror 2808 and a bluecolor light reflecting dichroic mirror 2809.

Further, the green color light which has transmitted through the polymerdispersion type liquid crystal element 2814 is reflected by the greencolor light reflecting dichroic mirror 2808, is synthesized with the redcolor light, transmits through the blue color light reflecting dichroicmirror 2809, and is incident on the projecting lens 2819. The blue colorlight which has transmitted through the polymer dispersion type liquidcrystal element 2813 is reflected by a total reflection mirror 2806 andthe blue color light reflecting dichroic mirror 2809, synthesized withthe red color light and the green color light, and is incident on theprojecting lens 2819.

The projecting lens 2819 is constituted of a rear group lens 2816 and afront group lens 2818 and the emitting side diaphragm 2817 arrangedtherebetween.

The rear group lens 2816 of the projecting lens 2819 and the incidentside lenses 2810, 2811 and 2812 bring the emitting side diaphragm 2817of the projecting lens and the incident side diaphragm 2803 into arelationship conjugated with each other. Accordingly, among lightsincident on the projecting lens 2819, light of pixel which has notundergone a scattering operation at the polymer dispersion type liquidcrystal elements 2813, 2814 and 2815, transmits through the emittingside diaphragm 2817 and constitutes bright display.

On the other hand, part or almost all of light of pixel which hasundergone the scattering operation in the polymer dispersion type liquidcrystal elements 2813, 2814 an 2815 cannot transmit through the emittingside diaphragm 2817, and accordingly, the dark display is constituted.

In this way, optical image light projected from the projecting apparatusis brought into a state of substantially unpolarized light sincepolarized light is not utilized in display. That is, optical image lightincident on the transmitting type screen 703 is unpolarized light, andaccordingly, even when the transparent base member of the lightdistribution control element 100 constituting the transmitting typescreen, is provided with birefringence, there is solved the problem ofoccurrence of a fringe pattern caused by optical anisotropy of thetransparent base member and the change in chromaticity caused by thepolarized light dependency of the light distribution characteristics ofthe light distribution control element. That is, there may be used atransparent body having optical anisotropy as the transparent basemember of the light distribution control element, and accordingly, amore inexpensive material having a higher strength can be used.

As described above, constitution, in place of a film havinginconsiderable birefringence, that is, an inexpensive film having a weakstrength such as a TAC film, an inexpensive film having a high strengthsuch as a biaxially elongated PET film can be used as a member of thelight distribution control element and the transmitting type screen ofthe rear projection type display apparatus can be realized at a lowcost.

Here, an explanation will be given of the light distribution controlelement 100 used in the present embodiment. The light distributioncontrol element 100 is provided with a constitution similar to thatexemplified in FIG. 1 and FIG. 2. A flat biaxially-elongated PET filmhaving a thickness of 120 μm is used for the transparent base member101. According to the biaxially-elongated film, compared with anon-elongated film, tensile strength or impact strength is increased andphysical properties such as transparency and a range of temperature usedare remarkably promoted.

The light distribution control element 100 is fabricated by a methoddescribed below. A transparent adhering agent layer comprising apolyester-based hot melt adhering agent is formed on the surface of thetransparent base member 101 by 5 μm, a colored adhering agent layer inwhich 10 parts by weight of carbon black is blended to thepolyester-based hot melt adhering agent is formed thereon by 4.5 μm andthe layers are once solidified.

Transparent beads made by glass in a spherical shape having a refractiveindex of 1.935 (wavelength: 589.3 nm) and a diameter of 50 μm arearranged to disperse densely thereon and the transparent beads arepressed to the side of the transparent base member by a pressing platewhile softening the transparent adhering agent layer and the coloradhering agent layer in a thermostatic chamber to thereby embed andfixedly bond the beads into the adhering agent layers. The thickness ofthe adhering layers after fixing the transparent beads is about 21 μm asa total of those of the transparent adhering agent layer and the coloredadhering agent layer and about 58% of the diameter of the transparentbeads is exposed from the adhering agent layers.

A flat transparent acrylic plate which is optically isotropic and has athickness of 2 mm is pasted on a surface of the light distributioncontrol element 100 on the side of the transparent base member 101.Further, a Fresnel lens is arranged on the side of the transparent beads105 to thereby constitute the transmission type screen 703 and thescreen as the two-dimensional optical switch element is integrated withthe projecting apparatus 701 using the polymer dispersion type liquidcrystal elements and the mirror 702 to thereby realize the rearprojection type display apparatus as shown in FIG. 11.

When the rear projection type display apparatus is evaluated, thepolarized states of the respective pieces of color light projected fromthe projecting apparatus 701 coincide with each other as unpolarizedlight, and there can be provided high grade image having neitherstaining nor fringe pattern caused by the polarized light dependency ofthe light distribution characteristics of the light distribution controlelement 100 constituting the transmission type screen 703. Further, awide isotropic viewing angle is provided such that 60 degree both in thehorizontal direction and the vertical direction is achieved.

Unnecessary light incident on the transmitting type screen from outsideis absorbed by the colored adhering agent layer of the colordistribution control element, and accordingly, there is realized blackdisplay having a brightness as low as 0.5 cd/m² under a brightenvironment (vertical brightness: 3001x) and the high contrast ratio isachieved even under the bright environment.

Further, as the two-dimensional optical switch element in whichpolarized light is not used for display, there can be used a digitalmirror device (DMD) disclosed in U.S. Pat. Nos. 5,061,049, 5,083,857 orU.S. patent application Ser. Nos. 08/161832 and 08/171303 and so on.

The DMD, described above, is provided with an array of very smallmirrors corresponding to pixels supported by twisted hinges and addresselectrodes on a semiconductor substrate and when a voltage is applied tothe address electrode, the very small mirror is deflected or rotated byelectrostatic pulling force.

Accordingly, when incident light is reflected toward a projecting lens,bright display is constituted and when incident light is reflectedtoward light absorbing means, dark display is constituted. That is, thedisplay can be carried out by unpolarized light, and accordingly, likethe rear projection type display apparatus using the polymer dispersiontype liquid crystal element even when a transparent base member of alight distribution control element used as a transmission type screen isoptically anisotropic, there can be provided a high grade image havingneither staining nor fringe pattern caused by polarized light dependencyof light distribution characteristics.

[Embodiment 5 of Rear Projection Type Display Apparatus]

Next, an explanation will be given of a further rear projection typedisplay apparatus according to the present invention. Similarly to theabove-described embodiments explained in reference to FIG. 11, the rearprojection type display apparatus, described here, is provided with theprojecting apparatus 701, the mirror 702 and the transmission typescreen 703, and the transmission type screen 703 is irradiated with theprojected light beam 704 emitted from the projecting apparatus 701 viathe mirror 702 to thereby display an image; however, the constitution ofthe projecting apparatus 701 differs from each other.

One of essential points of the present invention resides in that imagelight incident on the light distribution control element 100constituting the transmission type screen 703 is made substantially tobe unpolarized light. Therefore, in the present embodiment, this isrealized by arranging polarization eliminating means for eliminatingpolarization between the light distribution control element and thetwo-dimensional optical switch element other than using a displayelement which can be displayed by unpolarized light as a two-dimensionaloptical switch element.

As the polarization eliminating means, there can be used an element forartificially forming various kinds of polarized light within a range ofintegrating a wavelength width, time or the like and mixing andaveraging these to thereby form substantially unpolarized light in viewof phase or a so-called pseudo-depolarizer.

As the depolarizer, for example, there can be used a depolarizer of Lyotin which quartz plates having a thickness of 2 mm and a thickness of 1mm with refractive index anisotropy Δn of 0.009 which are cut andpolished in parallel with optical axes, are integrated such thatretarded phase axes intersect with each other by 45 degree. By using thedepolarizer, there is constituted a substantially complete depolarizerwith regard to white color light. Further, there may be constitutedsimilarly a pseudo-depolarizer by laminating a polymer liquid crystalfilm or a phase difference film in which d·Δn is made sufficientlylarger than a visible wavelength when a film thickness is designated byd and refractive index anisotropy is designated by Δn.

As illustrated in, for example, a projecting apparatus shown in FIG. 30,such a pseudo-depolarizer may be arranged in an optical path after colorlights which have transmitted through the two-dimensional optical switchelements 807, 808 and 809 have been subjected to color synthesis. InFIG. 30, a pseudo-depolarizer 3000 is arranged in the projectingapparatus using the TN liquid crystal display elements explained in theabove-described embodiments.

Thereby, optical image light, in which polarized light can besubstantially eliminated can be projected on the transmission typescreen 703.

That is, the polarized states of the respective pieces of color lightprojected from the projecting apparatus 701 coincide with each other assubstantially unpolarized light, and accordingly, there can be provideda high grade image having neither staining nor fringe pattern caused bythe polarized light dependency of the light distribution characteristicsof the light distribution control element. Further, as the transparentbase member 101 of the light distribution control element 100, there maybe used a transparent body having optical anisotropy, and therefore, arange of selecting a material for the transparent base member 101 iswidened, and a more inexpensive material having high strength can beused.

Further, although according to the rear projection type displayapparatus, described above, the explanation has been given of thetwo-dimensional optical switch element of the projecting apparatus usingthe transmission type liquid crystal display element, the presentinvention is not limited thereto, but the switch element may be adisplay element of a reflection type.

Further, there may be provided a liquid crystal display element having adisplay mode not only of the TN mode but also of a VA (Vertical Aligned)mode, an ECB mode, an OCB mode, an STN (Super Twisted Nematic) mode orthe like, or a liquid crystal display element using ferroelectric liquidcrystals or inverted ferroelectric liquid crystals.

[Embodiment 1 of Liquid Crystal Display Apparatus]

FIG. 31 is a schematic sectional view of a direct sight type liquidcrystal display apparatus using the light distribution control elementaccording to the present invention.

The liquid crystal display apparatus according to the present inventionis constituted of a liquid crystal display element 1302, a backlightapparatus 1301 provided at a rear face thereof, a polarizer 1204 and ananalyzer 1214 respectively arranged on the rear face and a front face ofthe liquid crystal display element 1302 and the light distributioncontrol element 100 according to the present invention provided on afront face of the analyzer 1214.

The backlight apparatus 1301 can efficiently emit substantially parallellight and there can be used “a backlight integral member forelectro-optical display” disclosed in, for example, International PatentPublication No. 505412/1997 or International Publication No. WO95/14255.

In this case, there is used a backlight apparatus constituted of a lightsource 1201 comprising a cold cathode tube, a light guiding member 1202composed of a transparent acrylic resin, and a light collimating means1203.

As the light collimating means 1203, there can be used a well-knownelement, for example, an array of micro taper rods in a quadrangularprism optically coupled to the light guiding member 1202 shown in FIG.31. In this case, light guided by the light guiding member 1202 istotally reflected by wall faces of the micro taper rod once or more, issubstantially collimated and is emitted.

As the light collimating means 1203 other than this, a micro prism sheetor an array of micro lenses can be used. By using the backlightapparatus having such a light collimating element 1203, there isprovided irradiation light substantially collimated within 10 degree ofa half value angle.

The liquid crystal display element 1302 is provided with a firsttransparent substrate 1210 having a transparent electrode 1212 composedof ITO and an orientation film 1211 composed of a polyimide-basedpolymer, an orientation film 1207, a transparent electrode 1206 formingpixels, a second transparent substrate 1205 having wirings, notillustrated, switching elements of thin film transistor or the likeconnected thereto and a liquid crystal layer 1209 composed of nematicliquid crystals having positive dielectric anisotropy enclosed betweenthe two sheets of transparent substrates 1212 and 1210 connected via asealing agent 1208.

The liquid crystal display element 1302 constitutes a so-called TNliquid crystal display element in which long axes of liquid crystalmolecules in the liquid crystal layer 1209 are continuously twisted by90 degree between the two sheets of transparent substrates by carryingout rubbing processing to the orientation films 1207 and 1211 providedto the two sheets of transparent substrates 1205 and 1210.

The polarizer 1204 and the analyzer 1214 are respectively arranged at alight incident face and a light emitting face of the above-describedliquid crystal display element 1302 such that linearly polarized lightsorthogonal to each other are transmitted therethrough. There are usedthe polarizer 1204 and the analyzer 1214 in each of which TAC protectivelayers are provided on both faces of a film provided with a polarizedlight function by making elongated PVA absorb iodine, and the polarizer1204 and the analyzer 1214 adhere to optically couple to the transparentsubstrate 1205 and the transparent substrate 1210 respectively by anacrylic-based adhering agent.

The light distribution control element 100 is arranged at a front faceof the analyzer 1214. As the light distribution control element 100,there is used an element explained in Embodiment 1 of the lightdistribution control element. Although the light distribution controlelement 100 adheres to the analyzer 1214 by an adhering agent 1213 whichis patterned to surround a display portion of the liquid crystal displayelement in this case, the adherence may be carried out by filling aclearance between transparent beads of the light distribution controlelement 100 and the analyzer 1214 by a transparent adhering agent havinga low refractive index over the entire face thereof or both proceduresmay be used.

Next, an explanation will be given of operation of the above-describeddirect sight type display apparatus. In emitting light 1215 emitted fromthe backlight apparatus 1301, linearly polarized light which hastransmitted through the polarizer 1204, transmits through the liquidcrystal panel 1302 and is incident on the analyzer 1214. At thisoccasion, a polarized state of light transmitting through the liquidcrystal panel 1302 is changed by an electric field applied to the liquidcrystal layer 1209, and accordingly, by applying an electric fieldcorresponding to image information on the liquid crystal layer 1209, animage can be formed by controlling an amount of light transmittingthrough the analyzer 1214. Image light which has transmitted through theanalyzer 1214 is incident on the light distribution control element 100.

Most of light incident on the light distribution control element 100 isincident on the transparent beads of the light distribution controlelement 100 is converged by its refracting action and is diverged.

Here, there is a viewing angle dependency in a general TN liquid crystaldisplay apparatus and when observed in an oblique direction, there arecaused a reduction in the contrast ratio, conversion of a gray scale anda change in color tone. Accordingly, a range of providing an excellentimage quality is limited to a range in the vicinity of a front face.

Further, according to the color distribution control element 100, asdescribed above, when an angle of incidence of incident light isincreased, the transmittance is reduced by absorption of light at thecolored adhering agent layer. Accordingly, in light emitted from theliquid crystal display element 1302, light having a large angle ofincidence to induce deterioration of the contrast ratio, inversion of agray scale and a change in color tone is mostly absorbed by the coloredadhering agent layer.

In the meantime, light in the vicinity of the front face havingsubstantially an angle of incidence of 0 degree providing an excellentimage quality is transmitted therethrough and is isotropically diverged,and accordingly, there is provided an image having no change in colortone or inversion of a gray scale in a wide viewing angle range andhaving the high contrast ratio.

Further, according to the liquid crystal display apparatus, lightirradiated from the backlight apparatus 1301 to the liquid crystaldisplay element 1302 is substantially parallel light, and accordingly,when a rate of a light amount in an angle range providing an excellentimage quality is increased in the liquid crystal display element 1302.At the same time, an optical loss at the light distribution controlelement 100 is reduced and an efficiency of utilizing light isincreased, and accordingly, there is provided an image having the highbrightness and the high contrast. Further, the light distributioncontrol element 100 is provided with a high effect of reducing straylight produced by outside unnecessary light, and accordingly, darkdisplay having low brightness is realized even under a brightenvironment and an image having the high contrast ratio can be provided.

When the liquid crystal display apparatus having the above-describedconstitution is evaluated, there is no change in color tone or inversionof a gray scale in a range of a viewing angle of 80 degree, and there isprovided an isotropic and wide viewing angle having the contrast ratioof 100:1 or more.

Further, normally, according to a TN liquid crystal display apparatus,in order to ensure symmetry of the contrast ratio in the horizontaldirection, it is general to arrange the transmission axes of linearlypolarized light of the polarizer and the analyzer to constitute an angleof 45 degree relative to the horizontal direction of the display face.

However, according to the liquid crystal display apparatus of thepresent invention, by isotropically diverging image light having aviewing angle providing an excellent image quality in the vicinity of 0degree, a wide viewing angle is provided, and accordingly, even when thetransmission axes of linearly polarized light of the polarizer 1204 andthe analyzer 1214 are not disposed to constitute 45 degree or 135 degreerelative to the horizontal direction of the display face, the symmetryof the contrast ratio is maintained. Rather, in view of the polarizedlight dependency of the light distribution characteristics of the lightdistribution control element constituting the liquid crystal displayapparatus, the transmission axis of linearly polarized light of theanalyzer 1214 is to be arranged to substantially coincide with thehorizontal direction of the display face of the liquid crystal element1302.

That is, as shown by a schematic view of FIG. 32, the transmission axisof linearly polarized light of the polarizer 1204 is arranged in adirection vertical to the display face of the liquid crystal displayapparatus and the transmission axis of linearly polarized light of theanalyzer 1214 is arranged in a direction horizontal to the display faceof the liquid crystal display apparatus. Accordingly, the orientationdirection of liquid crystals follow the directions and the orientationdirection of liquid crystals on a side of the transparent substrate 1205is directed in a direction vertical to the display face of the liquidcrystal display apparatus and the orientation direction of liquidcrystals on a side of the transparent substrate 1210 is directed in adirection horizontal to the display face of the liquid crystal displayapparatus, or the orientation direction of liquid crystals on the sideof the transparent substrate 1205 is directed in the directionhorizontal to the display face of the liquid crystal display apparatusand the orientation direction of liquid crystals on the side of thetransparent substrate 1210 is directed in the direction vertical to thedisplay face of the liquid crystal display apparatus.

By constructing in this way, light incident on the light distributioncontrol element 100 becomes linearly polarized light having theoscillation direction in the horizontal direction relative to thedisplay face. In this case, as described above, by the polarized lightdependency of the light distribution characteristics of the lightdistribution control element 100, there can be provided the liquidcrystal display element having the viewing angle in the horizontaldirection wider than that in the vertical direction of the display faceand having brightness which is symmetric in the left and rightdirections. This is very effective in efficiently distributing emittedlight to an observer since generally in a display apparatus a viewingangle in the horizontal direction is requested to be wider than that inthe vertical direction.

[Embodiment 2 of Liquid Crystal Display Apparatus]

FIG. 33 is a schematic sectional view of another direct sight typeliquid crystal display apparatus according to the present invention.According to the liquid crystal display apparatus, a phase contrastplate 3100 is arranged between the analyzer 1214 and the lightdistribution control element 100 in the liquid crystal display apparatusshown in FIG. 31.

As described above, according to the light distribution control element100 constituting the liquid crystal display apparatus, by the polarizedstate of incident light, the light distribution characteristics, thatis, the viewing angle can be changed. The phase contrast plate 3100 usesthe property and is provided with the function of converting linearlypolarized light which has transmitted through the analyzer 1214 intopolarized light providing a desired viewing angle.

For example, when a quarter wave plate is used as the phase contrastplate 3100, linearly polarized light which has transmitted through theanalyzer 1214 becomes substantially circularly polarized light by theoperation of the phase contrast plate 3100 and is incident on the lightdistribution control element 100, and there is provided an isotropicwide viewing angle to the same degree both in the horizontal directionand the vertical direction.

Further, in order to provide lateral symmetry of the contrast ratio asin the general TN liquid crystal display apparatus, the transmissionaxes of linearly polarized light of the analyzer 1214 and the polarizer1204 are arranged at 45 degree or 135 degree relative to the horizontaldirection, as the phase contrast plate 3100, for example, a half waveplate is arranged in a state in which a retarded phase axis thereof isinclined by 22.5 degree to the transmission axis of the analyzer andlight incident on the light distribution control element 100 isconverted such that the oscillation direction of the linearly polarizedlight is directed in the horizontal direction relative to the displayface.

In this case, by only adding the phase contrast plate 3100 and the lightdistribution control element 100 to an existing liquid crystal displayelement, there can be provided a liquid crystal display element having aviewing angle in the horizontal direction wider than that in thevertical direction of the display face and brightness symmetrical in theleft and right directions. Generally, according to the displayapparatus, a viewing angle in the horizontal direction is requested tobe wider than that in the vertical direction, which is very effective inefficiently distributing limited light to an observer.

Further, the same effect is achieved even when a polymer laminated filmhaving a twist structure is arranged in place of the phase contrastplate 3100. Such a polymer laminated film is realized by laminating foursheets of phase difference films of PC films having a phase differenceof, for example, d·Δn=275 nm and the four sheets of phase differencefilms may be arranged such that retarded phase axes thereof are directedto the transmission axis of the analyzer by 5.6 degree, 18.9 degree,28.1 degree and 39.4 degree from the films proximate to the liquidcrystal display element.

Further, although according to the above-described embodiments, to makethe drawings easy to see, there is shown an example of a TN liquidcrystal panel in a monochromatic display as the liquid crystal displayelement, a liquid crystal display element in a full color displayproviding micro color filters to a transparent substrate may benaturally used.

Further, the display mode is not limited to the TN mode, but there maybe used a liquid crystal panel in a VA mode, an ECB mode, an OCB mode,an STN mode or the like. Further, in respect of the drive method, theremay be constituted direct matrix driving other than active matrixdriving in which switching elements such as thin film transistors areprovided.

As described above, according to the light distribution control elementof the present invention, there is achieved an effect of providing awide viewing angle without any deterioration in image quality caused byoccurrence of a fringe pattern even when polarized light is incidentthereon by using a transparent body which is substantially isotropicoptically or which is provided with uniaxial anisotropy having anin-face optical axis as the transparent base member. Accordingly, thelight distribution control element according to the present inventioncan be used as viewing angle expanding means of a display apparatusutilizing polarized light as in a liquid crystal display apparatus.

Further, according to the rear projection type display apparatus of thepresent invention, the transmission type screen is constituted of thelight distribution control element according to the present inventionand a Fresnel lens arranged on the light incident side to thereby makethe angle of incidence of projected light incident on the lightdistribution control element substantially 0 degree, a reduction in thetransmittance at the light distribution control element is restrainedand a bright display image is provided. Further, by using the singletube type projecting apparatus as the projecting apparatus, color shiftor staining caused by the light incident angle dependency of the lightdistribution control element is not produced, and accordingly, a highgrade image can be formed.

Further, in the rear projection type display apparatus according to thepresent invention, the polarized states of projected lights emitted fromthe projecting apparatus are made to coincident with each other in therespective pieces of color light to thereby eliminate staining caused bythe polarized light dependency of the light distribution characteristicsof the light distribution control element and provide a high gradeimage.

Further, the light distribution control element is provided with thebright and wide viewing angle characteristics when viewed at any angle,the effect of reducing stray light derived from outside unnecessarylight is excellent, and accordingly, display of the high contrast ratiocan be realized by realizing black display having low brightness evenunder the bright environment.

Further, in the rear projection type display apparatus according to thepresent invention, by using micro-lenses substantially in shapes ofconcentric circles as the micro-lenses of the light distribution controlelement and installing the polarized state converting element capable ofchanging the polarized state of light projected to the transmission typescreen, there is achieved an effect in which without changing theconstitution of the screen, the viewing angle characteristics of thedisplay apparatus can be easily changed.

Further, by adding the observer sensing unit for sensing the presence orabsence of an observer, the observer position determining means fordetermining the positions of the observer in the horizontal and thevertical directions by the sensed signal of the sensing unit and thecontrol signal outputting means for outputting the control signal topolarized state converting element based on information of the positiondetermining means, to the rear projection type display apparatus tothereby automatically determine the positions of the observer and changethe polarized state of the projected light, the viewing anglecharacteristics in accordance with the positions of the observer can beachieved. That is, the viewing angle characteristics are automaticallychanged in accordance with the positions of the observer, limited imagelight can be effectively distributed to the direction of the observer,and accordingly, there is achieved an effect in which the observer canbe provided with an excellent image at an arbitrary position.

Further, according to the rear projection type display apparatus of thepresent invention, by constituting the projected light by the projectingapparatus, which is incident on the transmission type screen byunpolarized light, there can be provided a high grade image havingneither staining nor fringe pattern produced by the polarized lightdependency of the light distribution characteristics of the lightdistribution control element.

In this case, a material having optical anisotropy may be used for thetransparent base member of the light distribution control element, andaccordingly, a range of selecting the material is widened and there canbe achieved the transmission type screen using a more inexpensivematerial having high strength at a low cost.

Further, according to the liquid crystal display apparatus of thepresent invention, by arranging the light distribution control elementaccording to the present invention on the surface side and using thebacklight apparatus emitting the substantially parallel irradiationlight, only light in a range in the vicinity of the front face can bediverged isotropically by the light distribution control element, andaccordingly, there is provided the liquid crystal display apparatus ofan image having no change in color tone or inversion of a gray scale andhaving a high contrast ratio in a wide viewing angle range.

Further, in the liquid crystal display apparatus according to thepresent invention, by constituting light incident on the lightdistribution control element by linearly polarized light having theoscillation direction in the horizontal direction relative to thedisplay face, the viewing angle in the horizontal direction is madewider than that in the vertical direction of the display face andlimited light can be effectively distributed to an observer.

Further, according to the liquid crystal display apparatus of thepresent invention, the polarized state of light incident on the lightdistribution control element can be arbitrarily changed by the phasecontrast plate arranged between the analyzer and the light distributioncontrol element, and accordingly, only by changing the phase contrastplate, a predetermined viewing angle can be provided by utilizing thepolarized light dependency of the light distribution characteristics ofthe light distribution control element.

Industrial Applicability

As described above, in the liquid crystal display apparatus according tothe present invention, there are provided the light distribution controlelement without any deterioration of the image quality caused byoccurrence of a fringe pattern and the display apparatus using the lightdistribution control element and having the high brightness, highcontrast ratio and wide viewing angle.

1. A transmission type screen comprising: a light distribution controlelement including a transparent base member, a number of micro-lensesdensely arranged on one face of the transparent base member and a lightabsorbing layer having very small opening portions substantially atfocal positions of the micro-lenses, the transparent base member beingconstituted of a transparent body which is substantially isotropicoptically or a transparent body having uniaxial optical anisotropy.
 2. Atransmission type screen as claimed in claim 1, wherein the transparentbase member is at least one of: a glass plate; an acrylic resintransparent plate; and a transparent film made of at least one of: apolycarbonate resin, a vinyl chloride resin, a polyester-based resin, acellulose-based resin, a polyvinyl alcohol resin and a polyolefin resin.3. A transmission type screen as claimed in claim 1, comprising thetransparent base member being constituted of the transparent body havinguniaxial optical anisotropy having an optical axis in a direction inparallel with a face of the transparent base member.
 4. A transmissiontype screen as claimed in claim 1, comprising a non-transparent layerprovided between ones of the micro-lenses to absorb any light whichattempts transmission in areas between the micro-lenses.
 5. Atransmission type screen as claimed in claim 1, comprising ones of themicro-lenses having refractive indices in a range of one of: 1.6 through2.1 and, 1.9 through 2.1.
 6. A transmission type screen as claimed inclaim 1, comprising ones of the micro-lenses having refractive indicesdiffering from one another.
 7. A transmission type screen as claimed inclaim 1, comprising ones of the micro-lenses being a transparent beadadhered to the transparent base member.
 8. A transmission type screen asclaimed in claim 7, comprising ones of transparent beads having adiameter equal to, or smaller than, a half of a pixel pitch.
 9. Atransmission type screen as claimed in claim 7, comprising ones oftransparent beads having 50-80% of a body thereof exposed to a lightincident side of the transmission type screen.
 10. A transmission typescreen as claimed in claim 1, wherein the variation in phase differenceproduced by the difference in progressing angle of light progressing insaid transparent base member after passing through said micro-lenses isequal to or smaller than a half wavelength.
 11. A transmission typescreen as claimed in claim 1, wherein said micro-lenses are shaped in arod.
 12. A transmission type screen as claimed in claim 1, wherein saidmicro-lenses are shaped in a sphere.
 13. A display comprising: a lightsource; and a transmission type screen including: a light distributioncontrol element including a transparent base member, a number ofmicro-lenses densely arranged on one face of the transparent base memberand a light absorbing layer having very small opening portionssubstantially at focal positions of the micro-lenses, the transparentbase member being constituted of a transparent body which issubstantially isotropic optically or a transparent body having uniaxialoptical anisotropy.
 14. A display as claimed in claim 13, wherein thetransparent base member is at least one of: a glass plate; an acrylicresin transparent plate; and a transparent film made of at least one of:a polycarbonate resin, a vinyl chloride resin, a polyester-based resin,a cellulose-based resin, a polyvinyl alcohol resin and a polyolefinresin.
 15. A display as claimed in the claim 13, comprising thetransparent base member being constituted of the transparent body havinguniaxial optical anisotropy having an optical axis in a direction inparallel with a face of the transparent base member.
 16. A display asclaimed in claim 13, comprising a non-transparent layer provided betweenones of the micro-lenses to absorb any light which attempts transmissionin areas between the micro-lenses.
 17. A display as claimed in claim 13,comprising ones of the micro-lenses having refractive indices in a rangeof one of: 1.6 through 2.1; and, 1.9 through 2.1.
 18. A display asclaimed in claim 13, comprising ones of the micro-lenses havingrefractive indices differing from one another.
 19. A display as claimedin claim 13, comprising ones of the micro-lenses being a transparentbead adhered to the transparent base member.
 20. A display as claimed inclaim 19, comprising ones of transparent beads having a diameter equalto, or smaller than, a half of a pixel pitch.
 21. A display as claimedin claim 19, comprising ones of transparent beads having 50-80% of abody thereof exposed to a light incident side of the transmission typescreen.
 22. A display as claimed in claim 13, wherein the variation inphase difference produced by the difference in progressing angle oflight progressing in said transparent base member after passing throughsaid micro-lenses is equal to or smaller than a half wavelength.
 23. Adisplay as claimed in claim 13, comprising plural optical switchelements for modulating lights from said light source into optical imagelights according to incident image information, said optical imagelights being polarized lights, wherein polarized states of said pluralpolarized lights modulated by said plural optical switch elements aresubstantially coincide with each other when said optical image lightsare projected onto said transmission type screen.
 24. A display asclaimed in claim 23, wherein the polarized state of each of said pluralpolarized lights is circular polarization when projected onto saidtransmission type screen.
 25. A display as claimed in claim 23, whereinthe polarized state of each of said plural polarized lights is ellipticpolarization when projected onto said transmission type screen.
 26. Adisplay as claimed in claim 23, wherein the polarized state of each ofsaid polarized lights is linear polarization when projected onto saidtransmission type screen.